There's nothing wrong with investing in a 64bit platform today, believe me, if I had unlimited resources I would do it in a heartbeat. However, The Athlon64 platform that is available today will not be compatible with the athlon64 platform of early next year. The pin layout will change. If you get Athlon64 today, you wont be able to upgrade later. You will have to either buy a new mobo/cpu or upgrade to a duron. Like I said, theres nothing wrong with going for it now, but if money is a factor that you must consider, you will be better off waiting a couple months. I mean It's not that long of a wait. I am mostly getting this from the anandtech article posted yesterday. You guys should check it out.
As for me, I recently dropped 2 grand on a brand new setup (athlonXP2400, Epox 8rda+, 256MBddr, Radeon9700pro) to replace my previous system (P150 massively overclocked to 166, Voodoo3 3000, 256MB SIMM). The next time I get a new rig will probably be when DOOM/HalfLife2 come out, so like somewhere around Q4 2010 - Q1 2015.
phill9700,
I doubt AMD will steer in the direction of BTX, since AMD more-or-less targets the enthusiast market, whereas BTX is more-or-less meant for the "gramma's e-mail checking box" market.
Mainly, AMD wanted to do the new pin layout from the start, but just didn't have time. So they just basically rebadged the opteron, with a couple improvements, and called it the FX, what they plan to do early next year is what they initially wanted to do now, but didn't have time. Check out that anand article, he talks about that and explains it better than I can.