In addition to the tax cuts expiring in 23 days, emergency unemployment benefits expire January 2. I think I read that 2 million workers will be cut off if Congress does nothing.
Also, if no action is taken, 2% will be cut from Medicare as part of the sequester, other important social programs will be cut, the payroll tax holiday will expire, and many middle class families will get hit hard with the AMT if no patch is passed.
Most alarming, if no doc fix is passed, doctors will face a 40% cut in the reimbursement rates from Medicare, which will drive a lot of doctors to stop accepting Medicare if there is no fix. That may not happen right away but it's a big problem.
Oh yeah, and there's the debt ceiling fight coming up in February.