Theoretically, yes.

But this kind of attack would require an individual person to mine a specifically forged block (which takes extremely long, with today's difficulty), and then right at that moment, immediately double-spend the money at some retailer, before the rest of the network finds the next block. Seems like a *very* slim chance to me. Somebody would literally have to spend months outside a retail shop, trying to mine his specially prepared block, and then once he does, quickly go in and double spend some cash. Definitely not worth the trouble to buy some groceries or paying for a diner. As long as you require at least 1 confirmation for considerable amounts of money (e.g. buying houses or cars), I wouldn't consider this a real threat.