I find the comment on converting to 4e not just from 3.x but earlier editions encouraging.
For one, I have a lot of 2e material, but a lot of it just laid around unused during 3e because of the effort involved in converting. Maybe if adapting older material to 4e isn't difficult, that would be a good thing.
Also, I don't know about anyone else, but I'm getting really antsy here creatively. I'm feeling the urge to work on a new campaign world, but I put it all on hold when I first read 4e was going to be released. That was a few months ago, and that itch to create is getting damn unbearable. I felt it would be best to wait and see rather than start making something now that I'd have to go back and rewrite. I had a few problems like that with 3e, I used a campaign designed originally in late 2e, but some stuff did not convert well. Maybe this will be different, I don't know. Even then, there's some stuff that I'm still clueless on, like clerics, magic items, and I feel I'll have to hold off on it.