The capacity for a filibuster by Republicans will be destroyed ...
Prepare for some extremely Democratic legislation. (In the party sense, not the democracy sense).
As if. The Democrats simply aren't a solid bloc the way the Republicans have been in similar situations. And Arlen Specter may be becoming a Democrat but he's not becoming a liberal. Democrats don't tend to be united, and they give in to the other side pretty easily at times. I don't think this will change much at all, other than that it will be slightly easier to blame Democrats for everything that goes wrong over the next 4-8 years.