Burn-in on Plasmas hasn't been a problem for years. Our Plasma is 3 years old and the problem had pretty much phased out 2 years before we bought our TV. Plasma's do give better picture quality, but they are heavy and cumbersome to move.
I also read that TV's aren't necessarily cheaper before or after the superbowl (based on past comparisons). The prices on TV's drop as newer models come out.