<< 415-D (formerly 220-D never released) >>
No. 220-D was released, no boards were made using it. Let me clear this up:
420: Integrated Video, Twinbank architechure
415: No-integrated Video, Twinbank architechure
220: Integrated Video, no twinbank
And then if any of these have -D added, that means they have DD 5.1 support.
As for the future of NForce, well, the future in the enthusaist market is 415-D, and Here are the boards I've heard of so far, but more are on the way:
Asus A7N266-C
MSi K7N415 Pro
Leadtek K7N415
And more are supposedly on their way. There will also be sometime this year a new nForce that will supposedly feature a GF3 (or prolly GF4) MX core, and support PC2700 DDR, but don't expect this to perfom like a GF4MX because it won't even have the same bandwidth as a GF2 GTS so, but that's what's upcoming for nForce.