There is no doubt among the experts I've reviewed that it is authentic. Regarding the 'red' state threat. Remember a goal of this tape was to influence our election through a terror threat. That doesn't rule out any state.
It probably was authentic, in retrospect- but I was struck by several features:
too plump and healthy looking (unless he received a new kidney)
plump nose
no guns
too many comments about the US election
mistakes regarding how many died in 9/11
no Zawahiri by his side
no sign of aging since last tape
minimal quotes from the Koran(even in the deleted parts)
However--perhaps he has had access to excellent medical care and is now presenting himself more as a statesman than a warrior.