|"How much longer do you think this PC will survive with the demands on the processor, memory, etc... keep going up in demand?"|
Unfortunately Chris, you are the only one that can answer that question! Because, depending on how you want to use your computer, it might be time to upgrade now OR your system might be sufficient for another 2 years or more.
But for the sake of argument I will assume that gaming is the most intensive function that you are using your computer for. If that is the case, then continue to use your computer until your system will not support the new games you want to play or the quality is below what you find acceptable. With the system specs you have, I agree that spending a ton of money on a great video card is unwarranted because your processor will become the bottleneck. Also, as Avun pointed out, your upgrade paths will be limited due to the "retail" box that you have. The power supply may be proprietary - if so it can not be upgraded. And, even if you could upgrade the PS and but a top-of-the line Video card, you may only be able to upgrade to a 2.4GHz processor depending on the Front Side Bus that your motherboard supports (that is the fasted CPU my board supports). All in all, any upgrade you can perform would likely be short lived. However if an upgrade to a budget video card will allow you to play BF2, then that would be a small price for extending the life of your machine.
Personally I have a P4/2.4GHz and a GeForce FX5700 w/256MB Ram (the minimum card for BF2, but with more memory). I get acceptable performance in BF2 but am currently considering upgrading to an entirely new machine.