Re: Open Source...
Officially it will not support legacy hardware.
Unofficially the final source code is still not released. No one who knows how to do a port will (or should) make a pronouncement on whether or not porting Open Source to legacy hardware like Pre 3 is even workable. It all has to wait until the full source code is released... Plus time to investigate the code, trial and error, alpha, beta, how to instructions, work on your part... IF it even/ever happens at all.
There is absolutely no way the definitive answer will come in the next 24 hours.
Still: I say if you trust the source and it is a good price, get the Pre 3 and enjoy working with it for what it is... Not what it might, sorta, possibly, maybe could become.