It all depends on what they do with it.
In a lot of ways, MF is more suited to compact, professional-level bodies than full-frame is, since it's expected to do less things. No-one's going to be shooting fast action with MF, so it doesn't need strong AF capabilities and suffers less from viewfinder lag.
Basically, MF is restricted to shooting things that aren't moving very much or very fast. Which is still most things.
The problems, though, are lens selection and sensor size/aspect ratio.
Full-frame uses a 3:2 aspect ratio, which, all things considered, is a pretty good compromise (although 16:9 would probably a better ratio these days). Those shooting portraits often want 5:4 or square, videographers want 16:9, cinematographers 21:9, landscapers generally 3:2 and upwards, and events/action cover the whole gamut. Thing is, not everyone has the same resolution requirements - those shooting wider formats are often more in need of resolution than those shooting squarer formats.
If you shoot predominantly squarer formats, 44x33mm probably works well for you. If you're shooting 4:5, square format or other low-aspect ratio formats, you're getting an 89% increase in sensor area over what you could manage with full-frame (i.e. at 4:5, 41.25x33 is 89% larger than 24x30mm on full-frame, and, at square format, 33x33mm is 89% larger than 24x24mm).
Things don't work so well if you shoot wider. When the 44mm length is the limiting factor and you need to crop the shorter edge, you're only getting a 49% increase in sensor area. At 3:2 (29.3x44mm), 16:9 (24.75x44mm), 1:2 (22x44mm) or 1:3 (14.7x44mm) you're only gaining 49% image area over what you could have gotten from a full-frame image.
Fortunately, landscapers often have the ability to stitch. Those shooting wide panoramas may get screwed over by the aspect ratio, but, when stitching, you can create any effective sensor size and any aspect ratio. In fact, the only thing you really gain from the 44x33mm format is the 16-bit RAW file. The difference in resolution and effective sensor size can easily be made up for with a few extra shots - many of my 1:3 aspect ratio panoramas are made using a tilt-shift lens, with an effective sensor size of 24x60mm, cropped to 20x60mm. I suspect landscape shooters will just continue to stitch, rather than spending money on a system that only offers them a small increase in sensor area and far fewer lenses. It would be different if they released a 41x56mm (i.e. true 645-format), 24x65mm (X-pan) or 24x72mm (two full-frame sensors side-by-side) sensor, but the 44x33mm sensor really doesn't offer enough to landscapers shooting 3:2 and wider to offset the downsides.
Which leads to the next problem - lens selection.
Full-frame is one size - 24x36mm - so it's easy to design a lens that can go on different mounts and be used on a multitude of cameras. Medium format has a plethora of formats - 44x33mm, 45x30mm, 56x36mm, 54x41mm and 56x41mm - and that's just counting the ones up to 645-size. Which likely means a multitude of different, incompatible lenses, each designed for a different mount on a different aspect ratio.
An 'ultimate' MF landscape camera system would be very easy, though. 24x72mm (two full-frame sensors side-by-side), with a movable/tiltable back for tilt/shift capability with all lenses. Then just four zooms - 22-44mm f/5.6 (equivalent to 11-22mm in full frame along the longer dimension), 45-135mm f/5.6 (23-67mm equivalent), 135-400mm f/5.6 (67-200mm equivalent) and, optionally, a 300-800mm f/8 (for those long shots). A full system that covers every possible landscape, in MF size, that fits in a bag.
