They may reject Obamacare, but (IIRC by law) they are mandated to accept any patient, regardless of the ability to pay.
So, they will be hurting themselves by rejecting Obamacare.
Once a patient is admitted, however, they might be able to revert to Medicaid. Guess who gets stuck with those bills at the finale?
“they are mandated to accept any patient, regardless of the ability to pay”
But only for care specified under EMTALA and only until stabilization (more or less).
http://en.wikipedia.org/wiki/Emergency_Medical_Treatment_and_Active_Labor_Act