I'd serisouly contend that the RROD problem has drastically been addressed since about last May (that is, consoles made in May, not consoles on the shelf in May) since they have put in a much better heat sink, better DVD drives, better fans, and better X-clamp on the motherboard. I think regardless if the CPU was 65 nm, the actual problem is the GPU; so it is still 90 nm (which I think it is as of now), it'll still generate the same amount of heat. However, these fixes I described go a very long way to fixing the RROD problem (in my opinion, probably bring failure rates to a respactible industry level).
I bought a 360 in early August, and this system is very solid. It has all the additions to the hardware. I leave it on for hours at a time (I once accidentally left it online for 3 days straight...I was gone for a weekend, and somehow left it on) with no problems. It's much better at getting the heat out (you can feel the difference because the air coming out will be hot (which is good...out = good) while the air coming out of an older system, pre-May 07, will be cooler)). Honestly, I don't think it'l be as big of a challenge to land one of these newer consoles since the system has been selling like crazy.
If I were you, I would buy the holiday bundle that is coming late October. I'm not sure what you would get out of waiting, because I have a strong feeling the 360 isn't going to drop in price for a while (look at how long it took for the first drop: almost 2 years) and I feel like this bundle is their way of making a "price drop" (although it clearly isn't a price drop, you do get more for your money). I've also heard that this bundle may be a temporary holiday thing, so if you're interested in getting a couple of games thrown in with your system, then this holiday will be best.
Again, I'm not sure what you'd get out of waiting, other than missing out on some games this holiday. If you're not totally sure, it might be better to wait to see how the PS3 does; but if you think you'd enjoy the 360, late october when the bundles come out would definitely be the time to take the plunge; and I can all but gurarentee that these systems will have the fixes in their hardware (Falcon chip or not, it's the fixes I described above that really make the difference in overheating; and I can certainly bet that these systems will have these fixes).
Good luck!