kkonkkrete

Size and weight?  That's the key thing for me: a genuinely portable digital medium format travel camera.

^^^^ This
 
I bet it's possible to make a small, no frills MF travel camera with a sensor at least as big as the Pentax for 5 grand.

Given Fuji's background, a fixed prime lens (lenses) in 35mm equivillent focal lengths of 35-50 may be a simpler solution and if they opted for a square format say 45mm sensor as well... Try and do too much and you compete with the likes of Linhof, Sinar and Alpa in the simple technical arena, make an overblown X100 and you encroach on your own market, while a digital 6x8 would be so heavy and have to content with Hasel etc... but maybe they are going down a unique route rangefinder style, sliding back and dedicated stitching software to do 6x12 & 6x18 images!

30x45mm is correct for the likes of the Leica S2 but comparing the Hassy 40Mb against a D800 is definitely a slanted review (unless the point was to emphasis just how stupidly expensive the low end Hassys are, in which case - fair point). Note that the hassy has a removable back which allows a larger sensor to be fitted and comparing a low end MF back against the highest end DLSR at that time must be considered as a suspect review basis.
 
The key size for MF digital backs is standardising around the 53.9x40.4mm sensor sizes as used in Phase One's backs. From personal experience of using my Fuji's, my D800E and my Linhof Techno fitted with an IQ260 and Rodenstock lenses I can assure everyone the difference with a good MF sensor is just mind-blowing.
 
If Fuji are considering an MF camera i suspect it may be a challenger to the Leica S2 rather than a Hassy or the new Phase One XF. The S2 is a DLSR including the use of a mirror to permit an optical viewfinder. The big eureka moment for me and the reason I use my Fuji's much more than I use my Nikons these days is their digital viewfinder. A Fuji mirrorless MF camera makes more design sense than the bloated DLSR type Leica S2.
 
Which format should it be.... well my personal preference would for an MF X-E3 but the trouble Fuji will have is balancing the lens weight versus the body. With a mirrorless body the lens will drag the front end down. To solve this Fuji could go for a lighter lens design but that would mean slower apertures and in a world where photographers become addicted to using f/1.8 and higher, selling an expensive f/4 lens would be challenging.

They also had their own medium format camera in a rangefinder style.
 
I'd love for them to make a digital version of this....
 

0043 Fuji GW690III 90mm Professional 6x9 by Zebrio, on Flickr

Nah, Sony have FF in small package covered with the A7 and forthcoming A9 series.  I've got nothing against Fuji producing a FF --- sure, go for it.  But, I *really* hope they make a portable MF too.
 
See, what is absolutely missing from the market is MF sensor in small(ish) mirrorless format.  It's not a matter of competing with the existing MF market.  It's about creating a new market segment at a lower price point, stripped down to the basics in terms of interface and functions and, most of all ... portable.  I'm imagining a mirrorless MF camera that is smaller and lighter than a typical full-frame DSLR.  There were (and still are) analogue MF range finders.  Superb cameras that produce images that make even leicas weep with envy, which you can actually carry around all day with no problem.  Seriously, I would LOVE it if Fuji could make such a camera.  I'd even buy one with no freaking screen on the back if that helped keep costs and weight down (I know, crazy, but actually not being able to check every shot immediately makes me a WAY better photographer).  
 
Strip it down:
- manual focus only
- manual aperture control on the lens itself
- no screen (!) OK nobody else would probably buy this :-)
- a killer f/4 lens at 35mm FF equivalent (that's a 55mm on a 6x6 MF) ... trust me that's fast enough
- a BIG viewfinder like on a real MF camera

Ultimate Dream X camera(s): in no particular order:
1) A medium format equivalent to X100T, just scaled up. Would prefer a SQUARE sensor.
2) An E3 body with the largest size "APS" sensor possible relative to premium X lenses like 56/1.2 and 23/1.4. Would personally like this as a SQUARE sensor as well.
3) An E4 body with an ORGANIC sensor featuring the amazing sensor capabilities we've read about (resolution, dynamic range, etc.)
4) A simplified X camera with NO LCD SCREEN OR BUTTONS DIRECTLY ON BACK. Limited menus accessible via EVF only.
5) A standards-based lossless file format (PNG, JPG-2000).
6) Maybe a sensor based on some other alternate FUJI sensor layout patterns like the one with white as well as RGB pixels if it performs well, but forget about Bayer patterns.
7) Tripod threads should be relocated underneath lens axis, that's just plain silly.
8) If monochrome, would say in medium format only.

I'll have a medium format, square sensor camera.. thanks! :-)
 
+ tethered shooting! please!

MF Rangefinder!!!
 
Square format sensor!!!

Really, really hoping this rumour comes true.  The Sony alpha rumour of a Mamiya 7 style mirrorless medium format seems to have fizzled.  I wish the companies would focus more on larger sensor than ever more pixels in APSC and FF.
 
Medium format makes a huge difference to the look of images: the fall off away from the in-focus regions, the dynamic range, the sharpness, everything about medium format is godly, epic and monumental.  Environmental portraits look amazing in medium format.  They look like works of art.
 
I also really hope someone brings out a camera with a square sensor at some point.  Composing on a 6x6 analogue camera is a dream.  Yes I know you can crop afterwards, but it's not the same.
 
Please FUJI, make an affordable, *portable* digital medium format camera a reality!

Really, really hoping this rumour comes true.  The Sony alpha rumour of a Mamiya 7 style mirrorless medium format seems to have fizzled.  I wish the companies would focus more on larger sensor than ever more pixels in APSC and FF.
 
Medium format makes a huge difference to the look of images: the fall off away from the in-focus regions, the dynamic range, the sharpness, everything about medium format is godly, epic and monumental.  Environmental portraits look amazing in medium format.  They look like works of art.
 
I also really hope someone brings out a camera with a square sensor at some point.  Composing on a 6x6 analogue camera is a dream.  Yes I know you can crop afterwards, but it's not the same.
 
Please FUJI, make an affordable, *portable* digital medium format camera a reality!