In theory, yes. However, I wouldn't count on it in practice. For one thing, it will likely require a BIOS upgrade for the motherboard, and the MB manufacturer may not be willing to invest money updating the BIOS for a non-current MB model.
There may be other issues as well, so I wouldn't count on it until it actually happens.
ASUS has listed several of its boards that will work with a BIOS update. Probably other companies are doing the same. I'd personally wait for the new boards, as they will have better functionality with the new chips. Of course, since there are no Phenoms yet on the market, there is really no reason to buy a board yet.
Barcelona does has support in the QFX board, but that is not a common board, if you're thinking of going that direction. Again, a BIOS update would be good.