Many tend to get a bit too occupied with image quality and forget about compositional flexibility. Having just two or three fixed lenses without tilt and shift would make me insane, even if those lenses are great
I think you should at least consider the digital view camera case, Arca-Swiss F-Universalis and Cambo Actus are the cheapest to get new, but since you are a hobbyist and may not require around-the-clock support from a local dealer you may consider looking into ebay/for sale forums and make a great deal. It's a highly active second hand market for lenses, cameras and digital backs.
Considering the H50D-50c and 5Ds, the obvious advantage in terms of sensor is that you get a bit better DR, but Canon is not too bad these days so it's personal if you think the DR improvement is meaningful or not.
On the wide end Canon's TS-E 17 and 24 II impresses a lot, assuming you got a good copy. If you like to make large shifts I doubt Hassy's teleconverter+tilt-shift adapters will match.
If you don't think you will appreciate the movements of a tech camera I still think you should consider having shift capable lenses on the wide end, it's in the wide end the "leaning trees and buildings" are most evident (sure you can perspective correct, but you lose field of view and I think it's a less pleasing shooting process to leave composition to post-processing). The Hassy tilt-shift adapter is elegant, but very costly indeed, and as said I'm not sure it's really up to Canon's 17 and 24 anyway.
High resolving power is still quite new in the 135 format, but the interest from the market is large and we've already seen some new high resolution lenses like the Otus and Sigma Art range, plus Canon has been doing updates. There's a risk that if you go for the Hassy and has a lot of focus on image quality and value for money you will feel "hunted" by the progress in the smaller formats. If you get an interest in tech format for the reason of compositional flexibility (it's basically shooting with a large format view camera, but without having to mess with film) rather than only high resolution I think you can get more "peace".
Concerning the future of Hasselblad, it's anybody's guess. They've had bad economy for many years, but still they manage to survive. I wouldn't be surprised if they're out of business in five years, although I think it's more likely that they will make it, and actually I think the arrival of CMOS can become a success story. Even if they go out of business the camera would not instantly become worthless (or useless), just look at Contax, so I would not worry about the stability of Hasselblad as a company.
If I were you I would probably continue use the Canon for a couple of more years. Not only is high res genre new in 135 formats, but CMOS is new in medium format, so I think we can have some interesting technology progress in both format in the immediate years. Full-frame 645 (54x41mm) CMOS is likely to happen in both Phase One and Hasselblad in the next few years, just as Canon updates of the longer TS-E lenses (45/90). I also think medium format digital
will become less expensive, I think the price level seen in the current drive of the Hassys will be permanent in the next years, for two reasons. One is that competition from the smaller formats is toughening (similar image quality for a lot less money), the other is that CMOS is making the MFD cameras more all around and easier to sell to a larger group of people than before, making it possible with lower prices.
I can say one thing for sure, if you are not pleased with the resolving power you get from your current system, a H5D-50c will not make you much happier, the difference is too small. I think you'll need a 80 megapixel sensor and tech cam lenses to make any significant improvement there.
And of course, as some people already have mentioned, if you just want the 44x33mm Sony sensor, which many consider to be the best sensor available today, you should look at the Pentax 645z too.
