NOVEL INCOMING:
North Point Mall has certainly seen better days; the real death knell for it was the Sears bankruptcy and Apple leaving for it's own building at Avalon. Avalon and The Collection really didn't help either and both are absolutely thriving.
I can tell you that Alpharetta residents aren't going to really be gung-ho for a mixed use/arena development. 15 years ago? Absolutely, but not now. They enjoy downtown Alpharetta and the Avalon and don't really need a new hangout spot. And why support any sort of concessions if you can avoid the local traffic and let the people 5 miles up the road in Forsyth deal with it? Horrors, it takes 15 minutes to get there instead of 10! They tried this in Roswell at Holcomb Bridge (one exit south of the proposed arena) years ago and the people in Roswell said, "No, we don't want a mix of shopping and residences, we can either drive 20 minutes to The Collection or 20 minutes to Perimeter Mall or 20 minutes to Phipps/Lennox Mall".
I still think the MARTA expansion point is absolutely moot because a) no one in the northern suburbs is going to take it to and from games (because it just goes north and south, not east to west or west to east) and b) it's never going to happen (north Fulton residents and officials have routinely shot it down - they don't want it up there).
And this is all wholly, entirely ironic because the owners of the Atlanta Knights wanted to put an arena EXACTLY where North Point mall is before Ted bought a franchise. They knew north Fulton/Forsyth was a "print money" type of location.