Its not based solely on year nor is it based solely on processors. Certain models released in Late 2007 are still supported. The things that matter are:
64-Bit Intel Core 2 Duo processor or better required
Ability to boot into OS X 64-bit kernel
Advanced GPU chipset required
Not all Core2Duos have the 64 bit Kernel nor the GPU required. You have a Pro that likely does. The cutoff for pros was back in 2009 models at the latest (for the 13 inch). It goes back 2 years earlier for 15 and 17. TO better state things, if you have a Macbook, it can still run a modern OS for up to 4 years. The Pro even more - up to 6 and a half years (or 4 if you get the low end). The Air gets 4 years... and so on. The support you get is minimum 4 years.
Trouble is, we have no idea how aggressive the updates are going to be down the line. We have nothing to base things on at all. Nothing. I think you will be safe for about 3-4 more updates unless your Pro is the 13 inch model