Upgrade now or wait?

One or more parts on my Gaming PC are starting to fail. I'm looking to build a new one but I wanted to get some other opinions before I went gung-ho on a new build. I generally keep up to date on modern tech but I don't read into future advancements as much as I should. So I have one big question before I get started.

Are there any major technologies that are right around the corner? When I built my last machine, I tossed it together in an emergency like the one I'm in now. I missed out on DDR2 Memory and SATA drives that were just starting to pick up steam. While they aren't deal breakers, I don't want to make the same mistake twice.

Right now money is a little tight. Tax time next year should put me back into the "comfortable" range. If I need to wait, I have a personal laptop that I can use for basic web-browsing but it can't keep up with modern games. If waiting a couple months will help future-proof my machine a little bit, so be it.

There is always something newer and better coming, so what you build will be old not long after you build it. That's life in computers.

What do you have now?
What do you have to spend?
What games do you want to play?

Intel's Nehalem is coming soon, but initially that will likely be for $1500 and up builds. (Perhaps more, we will need to have to see Mobo and DDR3 prices. The CPU should go for just over $300 at release due to a "Tray price of $284 and initial demand which will keep it over the $284 price for a little while.)

The answers to Zenmaster's questions will be useful for determining good answers to yours.

I'm thinking for 700 bucks you could have a really nice system. That said, I think in your situation, put that 700 toward a nice rig now, because 700 is on a budget but if you have an OS to put on it, you can really put a quite decent tower together if you watch it. That said......I think build a tower now, keep the 19 inch, come next year, you can have saved a little, and then with your tax return go out and get yourself a nice 22 or 24 inch monitor, or whatever you can afford. At that though, you may almost be able to get a decent 26 inch lcd tv that may do well for games. Other guys will need to comment on that though.