I doubt I will make the switch with my personal campaign, however, I will be running a 4th edition game at the game store where I work part time depending on interest.
In terms of publishing, I haven't finalized all of my decisions, but for the time being DragonWing Games/Bastion Press will offer 3.5 material and 4e material when the time comes. The tentative plan is to release Book of Curses as a 3.5 pdf and a 4e print product. Sales of those formats will help determine future releases.