I'm sure 2010 is gonna be remarkable for her and her team as every year has been since she started with her concerts, etc. ^^ It might be just another year for a new album and the tour of it, or it could be as you said the year for her 50th single.
I don't think her 50th single is going to be that big, the fact that is the 50th single is what is gonna make it a big thing to release, and probably bring up another tour like the stadium tour (*o*) or she might wait until the end of next year and have a 50th single anniversary Countdown live etc which I wouldn't mind
I wanted another single before a new album, cause sunrise/sunset was pretty weak, and You were... with BALLAD ain't enough to make it seem interesting. so after that album, maybe another single for september, and the 50th single for november
I don't wanna expect anything from her new album, I just dunno what to expect anymore, I just want her to have fun with it and try to put more ideas into her new stuff and not just let her team to do everything.