I do too miss a lot shooting with my 50CM. Love the square for a lot of things.
Equally I care more for larger sensors than more megapixels. My minimun count would be 22, so when I crop to rectangular I couls still have 16mp or so. My minimun personal crop factor is around 1.25X, larger than that, doesn't cut it for me.
I do believe that larger sensors will eventually come. Just think abou it. If you come with a multi-million development like the Hy6/AFi, why make it 56X56mm if commercial sensors had topped their in size?
By all counts, designing from scratch an only-digital 48X48mm sensor digital MF system would be a lot easier and optimized from birth to this size.
It doesn't make sense to me they went to all that trouble just for film.
In my particular case, I would go into a only-digital system even with a reduced (from 120 film sizes) sensor. if it meant a better price.
I realize this is idle speculation, but I'm wondering if there is any reliable word of forthcoming square medium format sensors for cameras like the Hassy V, Rollei or Hy6? I was out shooting film with my Hassy 203 FE today for the first time in a long time and realized I'd forgotten how much I like shooting square with a waist level finder. I'm less interested in absolute megapixel count (16 or so would be fine with me) and more interested in a physically larger sensor than what's currently available (I believe all the square sensors that currently exist have a 1.5 crop, which I just wouldn't be able to live with).
Don't get me wrong, I'm not morally opposed to film or anything and since I'm now only shooting for personal work, I can use film when using the Hassy. But it would be nice to have a full format (or closer to full format) digital option. I'd imagine there has to be not-insignificant demand for such a sensor, especially in the price range of the P20 and CFV backs (which I believe are less than $10K).
I should add that I'm aware that Sinar is marketing the Hy6 with speculation about there "one day" being full frame 6x6 sensors. But I don't know how realistic or imminent that is thought to be, or whether it's just marketing hype.