What would actually happen if the DNC just seated the Michigan and Florida delegates. Pandemonium, right? Beyond the fact that all states and an assortment of territories followed the rules except Florida and Michigan, what would be wrong with giving them another vote anyway? Sure, it costs money; but, apart from the costs, the only issue is following the rules agreed to before hand. Now that's reason enough to be sure.
The argument that all states could ignore the rules thereafter actually isn't a valid argument. So what if all states could ignore the rules? It would mean the demise of the rule, which would be a good thing. The current rules are stupid and need changing. You want to make the states fair and fairly proportioned by populace? Just have one set of elections nationwide. One day. One vote per person. No counting of votes on the first day.
So this year let's follow the rules to which were agreed. Next year, let's do away with the rules and go for the right solution.
Some might say its difficult to implement. I'm certain it is; but, it can't be as hard as going to the moon with the technology of the sixties. Start in 2009 and it might be ready in 2012.