Welcome to the Ranch. As for your question... do you want more of a hands-on exam or simply MC questions? If the SCJP+ is really based on Java SE 7, which I doubt, you know the (potential) differences between the 2 versions?
Do you have information about when the SCJP+ exam will be available?
What we know for sure is that the beta was postponed, and that historically the amount of time required for a new exam to go from beta through to live is maybe 6 to 9 months. Throw in the release of Java 7 as another variable (when is that due to be live?), and I'd say you ought to go ahead and pursue the current exam.
I'll refine that advice a little... if you're already certified, and thinking about an upgrade, then perhaps the incremental change to SCJP 6 isn't that great and it might be wise to wait. On the other hand, if you're not certified, and you think you could benefit from a certification, I'd say that the difference between the SCJP 6 and the SCJP+ will be incremental, and personally, I wouldn't wait.
Spot false dilemmas now, ask me how!
(If you're not on the edge, you're taking up too much room.)