I was thinking about getting a P35, or possibly a X38. But since hearing that the P45 chipset is coming out, should I wait it out and see, or should I just settle for a P35?

All new stuff generally costs more, so I would go for a p35 if you can find one with the features you want for around $100.

It depends on your budget.
P45 will replace the upper P35 boards (around $150, like P5K Premium and the rest) and lower X38 (around $200) pricewise. Since you were considering X38 I'd go with that (X38 and X48 differ so little it's irrelevant). It's a bit easier to overclock 333MHz FSB processors with it as it does 400MHz FSB stock.