Is medium format a dying breed? I think of several answers, none of which are as flipant as they sound:
answer 1 - yes, but who cares?
answer 2- no, digital backs will save it (maybe).
answer 3 - yes, digital 35 in the 20 megapixel area will replace digital MF.
two years ago if you were buying a professional portrait/wedding/studio camera, it would probably smart to buy a medium format camera. image size/production costs were a good mix of quality/film-processing costs relative to 35mm and 4x5. and, as digital improves its price/performance, someone is going to make a digital back for my medium format camera.
thanks primarily to Canon and its high end digital camera, that answer is becoming less correct. if you're shooting digital, 35mm is beginning to look like a great way to go. quality and price will soon reach a level where it is sharp enough and cheap enough that a Canon is all you'll ever need for wedding photography. wedding photographers don't shoot 4x5 anymore - the increased quality is not necessary and MF wins in terms of ease of use.
since canon will sell far more 1Ds's than Kodak will DCS backs for a Hassleblad, inevitably, the price for a "good enough" (and i don't mean that in a bad sense) canon will be way lower than than the MF with a digital back. at that point, no reason for digital MF to exist, and soon, with no reason for digital MF to exist, then no reason for MF to exist.
But, who cares? I keep coming back to "digital is digital and film is film". the members of this forum understand the difference and judge film to be superior, and perhaps judge that it will always be superior for aesthetic or simply archive reasons.
I went through this scare 4 years ago when Kodak announced it was discontinuing the production of 5x7 film. This, after I had just completed my equipment setup including a new Omega enlarger. Four years later Kodak is still making 5x7 film and I realize that if they don't, someone else will.
Take a worst case, you are a 20 year old student and love B&W film. If you bought a 30 year old Leica M4 or Hassleblad 500CM today, because you couldn't afford something newer, by the time you are 60 the camera would still be repairable and there would be film available for it. For your own work, would you ever need better than an M4 with a 35mm Summicron or a 500CM with a 150 Sonar? Large format will survive even longer!
Be glad you got your beautiful yellow Hassleblad before they stopped making them and just enjoy taking pictures with it.