Will the BE300 boards fit into the Prisma fan/heatsink body?
Yes! That would be great since there are probably tons of prisma heatsinks and fans laying around with the buy-back. Since you would only need to ship the new boards, you can save money with shipping.
From earlier statements it appears that the power density of BE300 miners will be lower, and so won't need nearly the same levels of cooling. Sure if a few of the screw holes match up you could put them onto Prisma heatsinks but at this point it may just be overkill.
Considering the overall failure of the safety design of Prisma's, overkill may not be out of order in the cooling department. Besides, the move to 1KW+ miners isn't unwelcome, at least not in my case. Less miners, less cables, less points of potential failure...
Or ship the heatsinks, which would be an improvement as well.
Agreed, if only they were further in development. They could have made an upgrade/trade-in plan for Prisma owners instead of having to pay all shipping costs back, and presumably re-use the chassis and re-ship to customers. Such is life, by the time these are released I'll be ready to upgrade my Tubes anyways.