My take on things: the Brown win could cause the Dems in Washington to be less divided amongst themselves. Healthcare may not be over -- depends if they want to just go the reconciliation route and get a major piece of legislation on the boards. If they cave on healthcare now, they will have lost an entire year and the GOP will have an opening with voters both on economics and the Dems' fecklessness. I can see the ads now: "Why did the Democrats spend an entire year dawdling when YOU were out of work?? Take your country back..." and "Healthcare: they all voted for it before they were against it".
On the state level, Charlie Baker will beat Deval Patrick in November. Census figures will cause MA to lose one seat in the House. Baker will have a major say on the redistricting of MA's remaining Congressional seats and in doing so will try to clear out someone who cannot be a threat to Brown in 2012 (Tierney, Delahunt, Olver, Neal, Tsongas). After losing the Kennedy seat and the governor's race, MA Dems will finally have the fire back. And with Obama on the national ticket -- likely with a much stronger economy and further losses in the 2010 midterms, the Dems will have decent prospects in 2012.
I can see Mike Capuano, Marty Meehan and Barney Frank all as being able to beat Brown. Maybe Ed Markey. NO, no Dukakis, not EVER.