Ya they are completely unserious, which is a shame. It would be suicide for the Republicans to swallow a tax increase without any other changes. The Democrats get away with never proposing any sort of serious cuts. The focus is always on the red herring which is the top tax rate.
I would just let everything expire. The Democrats will still "sort of" win in that the Republicans will have to settle a partial reinstatement of the Bush tax cuts except for the top bracket, but at least they aren't directly raising taxes, the Democrats essentially are the ones raising taxes in that scenario.
And the Democrats are in power so they will more/less own the disaster of the markets crashing.