yep, i bet it will be possible, in theory. but a lone hacker will have to do it.
there's no way sprint would do it.
what do they gain?
the risk of having phones break on flash, or what if people don't like it.
they'll lose their contacts, etc..
sprint isn't going to want to help transfer them.
there's no reason for sprint to risk it.
they'll likely just release android on a new HTC phone as mentioned above.
I personally will do whatever it takes to get one.
i vowed i wouldn't get the iphone and their closed ideas, so this is my bet on the future.
remember, everything google does turns to gold