Agreed. Considering that the worldwide launch isn't going to happen until late May, that would leave a little over three months before a refresh. They'd be absolutely nuts to piss that many people off. It's not going to happen.
Whenever a new iDevice comes out, I usually purchase the highest-end model. That way, when the inevitable followup comes out, I can sell it and buy the newest version.
I think many people take the opposite approach- buying the lowest-end model- and when they try to sell it, they make little money because there is a flood of them.
I purchased the original iPhone about 6 months after it's launch. Since then, I've upgraded to the highest-end iPhone each year, day of release, and haven't spent a penny out of pocket. In fact, when I sold my original iPhone, I actually MADE money to upgrade.
Apple products hold their value very, very well. Once, I even sold a MBA that had been run over by a number of cars for $900! I expect the value-reatinment to be similar with the iPad.