according to rumors and leaks-
current ivb supporting pch: h61, h67, p67, z68 (will require a bios and driver upgrade)
not supporting: b and q series (corporate/executive pch)
ivb-specific pch: h77, z75, z77 (known so far).
you should wait for the platform to launch and then you (and the rest of us) can find out for sure if it works the way its rumored to work. latest launch rumor suggests around april 9 2012 or something.
intel hassn't been upgrade friendly in the past. it'll be interesting to see how this time works out.
check the ivb sticky in the cpu section. it is very informative.