Wait or do it now?

OK I'm looking to get into Windows phone, possibly to use as a second device (or possibly my primary device, if I like it that much). I really like the Lumia 900, but now people are saying things about Windows phone moving to a higher resolution and/or dual core, possibly at MWC. I don't know much about rumors for these types of things, so I was wondering if you knowledgeable people could give me some advice: do I get the Lumia when it comes out, or wait for whatever the next big thing is in Windows phone? One thing to consider is that I will have to buy whatever it is off contract and on AT&T.