Intel's not making any 7 core or 14 core parts now or in the near future (perhaps something not yet leaked or even designed *might* happen, but there's currently nothing on the roadmaps).
As per gaming, as mentioned, the additional cores won't be used. The load is on the GPU, not the cores. Most games are single core, and a rare game here or there might use 2. I've heard of 4 for a single game (can't even recall the title), but not sure if that information was even correct.
Your current machine is more than enough in terms of CPU power. Perhaps using Windows 7 on the MP and another GPU (Windows only; there are ways to power them if you're interested) would be the best solution vs. building a dedicated gaming rig in terms of keeping the costs as low as possible (though you could get past a single GPU via Crossfire or SLI, depending on your GPU/s of choice if budget isn't as much of an issue).