Pay as you go and Skype options. Can you get a Data only plan?

Now that we are coming up on the end of the original 2-year contracts, we know that a new phone is in the works (afterall, Apple just ordered 3.2M 5 megapixel iPhone cameras), and now I'm looking for options to both extend the life and reduce my bills on my phone. I pretty much use maybe 150 minutes a month, 50-100 texts, and grab email here and there.

So 2 question:

1) Does anyone know if you can easily switch to a pay-as-you go plan once you contract runs out (I know there was a way to do this at initial setup by entering 999-99-9999 as your SS#)? I'm thinking I can pretty much use that for accepting calls and then use Skype any time I'm near a WiFi hotspot to call for 2 cents a minute.

2) Can you drop your voice plan and just keep the $20 a month data plan?

 

I know right now there is not, but once my contract is up, I wonder what will happen if I call and just try to cancel the voice.