I'm quoting my own 2/28 post:
My prediction: Zeta will go forward (now that it's been revived) and serve as the basis of a new Camaro, and then that same platform will give rise to a Pontiac of some sort. I suspect, though, that it won't be a Firebird twin--it'll be a GTO.
I've read that GM has already fast-tracked the Camaro by moving it ahead one model year (from '09 to '08, I believe). GM oversaturated the pony car market with both a Camaro and a Firebird as their counterweight to Ford's Mustang, so I think that if Pontiac is to get a rear wheel-drive performance car, it'll be more along the lines of a GT. A GTO would fit the bill.