after 9 months I don't think you'll be able to trade it in. Normally you have to have completed 20 months of a 24 month contract. There is an annual upgrade after 12 months, but there are stipulations on it and I'm not 100% on what they are.
Verizon doesn't offer the Pre. When they do it still won't be the Palm OS. The Pre runs WebOS. It's a different operating system. But no, when they do you will not be able to trade-in your Storm. If you're eligible for an upgrade in Q1 of 2010 then you can purchase it when the Pre is released.