If it were guaranteed that intel were not gonna do anything about the recent market share loss to AMD i think it would make sense for AMD to go for it near term. However, Intel is soon to have a competitive product for a change and I think it would be very foolish on AMD's part to go on a mad expansion spree on borrowed money. If they were to go that route, Intel could undercut AMD prices and destroy their margins. Then all of the sudden, they are deep in the red every quarter and start having to cut budgets like say for instance R&D. The wiser choice would be to ramp up fab 36 and see what happens to their market share once intel's new products are released. If they continue to gain share against conroe and company then I would say expand. But not before.
In other words, they need to keep their expansion slow and steady. Trying not to expand too much on money they havent made yet. Trying to go too fast could end up burying them.