It's worth the wait if you're doing tasks which are hungry for more threads. But without knowing what you intend to do with the PC, we can only give hypothetical answers.
There is always something faster or better just around the corner. But you need to decide if you truly need (or just want) the extra capabilities of the i9.
Q1 2010, but if you know the right peeps you can get one now. Also i would wait for it, cuz even if you dont need it the price of everything will drop when it comes out.