Re: System Longevity...
If you plan on buying an i7 then don't waste any money on your current build. If you're serious about upgrading your current build go for it, but if you want a completely new one just live with the current one for a year or two. You know I lived with an outdated build for 3 years, I didn't upgrade it because there was no use putting money into a PC that had no more potential and I knew it would be much better to wait until I had enough to buy a good new PC. It took a while but it definitely paid off.
Plus your current build is godly compared to my old PC, your current build should have no problems with many modern games (you know Team Fortress 2 is fun, admit it).