It's important for Durbin (and Pelosi, et. al.) to keep publicly reiterating what a terrible idea this is and putting pressure on the administration not to make this concession.
Krugman, in typical style, lays it out plainly (emphases mine):
I'm going to cross my fingers and hope that this is just a case of creeping Broderism, that it's a VSP fantasy about how we're going to resolve this in a bipartisan way. Because if Obama really does make this deal, there will be hell to pay.Yeah.
First, raising the Medicare age is terrible policy. It would be terrible policy even if the Affordable Care Act were going to be there in full force for 65 and 66 year olds, because it would cost the public $2 for every dollar in federal funds saved. And in case you haven't noticed, Republican governors are still fighting the ACA tooth and nail; if they block the Medicaid expansion, as some will, lower-income seniors will just be pitched into the abyss.
Second, why on earth would Obama be selling Medicare away to raise top tax rates when he gets a big rate rise on January 1 just by doing nothing? And no, vague promises about closing loopholes won’t do it: a rate rise is the real deal, no questions, and should not be traded away for who knows what.
...And if it does happen, the disillusionment on the Democratic side would be huge. All that effort to reelect Obama, and the first thing he does is give away two years of Medicare? How's that going to play in future attempts to get out the vote?
If anyone in the White House is seriously thinking along these lines, please stop it right now.