Depends on the market. There are markets that are already on the point of popping, due to refinancings and homeowners and mortgage companies finding appraisers who are pushing values way to hard.
A good indicator of when a market is going to pop is watching sales. When you start seeing houses staying on the market for over sixty to ninety days, then it is over priced, and thus the market is getting top heavy. You see a proliferation of these, and you know not to invest.
Everybody wants top dollar. Unfortunately, it is not an infinite liimit.