Maybe if there will be a boom on coins using a GPU bound algorithm. I think the probability for that is pretty low.

GPUs aren't designed to be running on a 100 % capacity for a long time. A GPU will break pretty fast simply because it isn'n designed to take all that heat. Those algorithms that are the most profitable on GPU are really memory intensive so especially memory heats a too much. If you invest on a GPU it may not last so long that it would ROI.

An asic chip could be desinged for every algorithm so as mining business gets bigger we will also have asics for those memory intensive algorithms that are used to be mined on GPUs today. Also a lot of GPUs are already out there. I have a few and I only can gain a little more than I pay for electricity. My GPUs have already paid themselves back but if I bought one today, it probably won't.

Buying a GPU like any mining hardware today is speculation. One could as well buy coins and profit more.