I think most players in that game are going to pay off with A5, AK, A7, or A4. AK, A7, or A4 are only reasonable if you think he was trying to get more calls on the turn (and if the Ace on the turn did not create a flush draw).

This is highly player dependent, and in a live game it's hard to judge that kind of stuff without sitting at the table. A call is obviously a fine play, and carries little risk. A lot of the time I'm going to raise him all in and hope to see a slow played AK or A5. But without a specific read I think I'm going to just call. If you just call at least you will get to see his cards and will have more information on him next time. If you raise you only see his cards if he has you beat...