Yes, like any other commodity the market can overheat due to speculative activity increasing far beyond normal demand. However, each wine is produced in a finite amount, there are emerging markets in China, India and Russia (not to mention countries like Brazil just over the horizon) to provide demand. In addition each five star hotel in the world will need to hold a selection of top end wines. So we are not looking at the 17th century Tulip bubble.
On current trends we are likely to see a bubble limited to a particular wine, or sector of the market. However, as wine investment becomes more main-stream and more speculators move into the market who knows what may happen.