As a Tour user myself, I personally would jump on getting it ASAP, because I just CANNOT stand my BlackBerry. Plus, it's not definitive that Verizon will get whatever Apple releases in June... but it's up to you. My update's not until April 30, so I'm waiting...
If I were you, I'd figure out what you use the phone for the most, and if the iPhone's going to make that more enjoyable, I'd switch. If it's not going to change too much, I'd hold out.
Just my 2¢
