Still in a 'wait and see' mode. However, I can tell you what I'll be doing with any ongoing campaign when the time comes...
Shortly after the announcement, an element of 4e was revealed that was an absolute deal-breaker for me. I'm still hopeful it may be changed, although I haven't heard anything to that effect thus far. If it is not changed, I won't be buying 4e.
If that element is changed, then I will buy the 4e core rulebooks (in support of that decision if nothing else). I'll then decide whether to switch over or not. Sadly, it looks like the answer is 'not', since I've actively disliked more of what I've heard than I have liked. But I will, of course, reserve the final judgement until I see how the whole thing looks.
If I do switch, I won't be attempting a conversion - the campaign will run to its natural conclusion, and then I'll start a whole new campaign under 4e rules.