While there may be a lot of old film SLRs sitting in storage, (and how much is there really? How many people do you know that still have an old 35mm SLR kit?) I still don't think they would get much use. Remember, the common consumer probably won't ever want to go back to the bigger and bulkier SLR setup when they have grown accustomed to their compact P&S. It's not about image quality, usability, features, etc. for them- it's all about convenience, portability, and instant results. They also wouldn't be able to do image review, which means a shooting discipline likely greater than the vast majority are willing to dedicate themselves to.
For the photography enthusiast who's looking to upgrade from his film SLR or get back into shooting after a long hiatus, well they probably are looking for some more modern features in their new camera- matrix metering, autofocus, high speed frame capture, etc. Also cost-wise, again unless it can significantly undercut the cost of an entry level DSLR, (at which point it probably undercuts a lot of P&S too, which is a pretty outlandish concept) well then it doesn't make much sense to keep using that old gear when you could upgrade to a vastly more modern setup at a comparable price.
That cuts out probably >95% of film cameras in storage.
Beyond that, you have the retro people who enjoy using the old gear for the sake of being retro or to be cool. This would work for them, but is there enough of a market? Because the market would be small, the price would be high. Would you pay the equivalent of a good prosumer DSLR body (think $1000-1500) just to be able to use that old Holga?
Ruahrc
I think a re35 system needs to be aimed at enthusiasts primarily. There may be some buyers from the "consumer" market segment, but I think they would be the minority. The real market are the enthusiasts, who have a good reason (for them) to want to dust off hold equipment. For example
1) Pure manual. Manual exposure, manual focus, non-zoom/prime lenses (so you have to 'manually' switch focal lengths, or 'manually' walk closer).
2) Specialty lenses. Scientific grade macros, ultra fish-eyes, bellows, tilt and shfit, 500mm reflex lenses. Many of these are just not affordable (if available at all) in modern cameras)
3) Old glass. Lovely and soft. And often very fast.
4) The chance to use incredibly quirky machinery from the early days of 35mm.
5) The chance to use incredibly engineered, non-electrical machinery from the early days.
None of these potential customers are going to comparing the price of a re35 to a modern digital system. They will pay more than the average consumer. I believe considerably more in some cases. If I have several old cameras (I don't - I have several
dozen 
) I only need to buy one re35 to resurrect all of them.
I think something like this can be priced in a way that Polaroid failed to do. Polaroid thought their entire competition was digital (and it was, but only for a portion of their business)... so they priced themselves down to the point they couldn't turn a profit. They never clued in that they could have priced
up, lost the same number of people to digital that they were going to regardless of price, but kept turning on profit selling to those of us who were using Polaroid material - not instead of digital but - because we liked using it for itself. We would have paid more (complained, yes! But still paid) for Polaroid stuff.
I think the re35 system is like that. They could charge a higher price, and still sell enough to make a profit. There are enough of us out there who would pay quite a bit for to have some very interesting creative doors opened.
And to answer your question. Yes, I would pay nearly $1000 for something that allowed me to use just about
any 35mm system I may already have, or could go out and buy because they are cheap and it has lense I want to use.
@emorydunn"My dad's been saying someone needs to make a BW only conversion kit for years. In fact, at one point we were talking about something almost identical to the re35 (if only we'd beat them to the punch with the joke)."
Maybe not quite what your dad has in mind, but check out the PhaseOne Achromatic+ back
(Link)