I see it that:
1. Pop Century is very popular with many guests and there will not be a drop off.
Definitely possible. Time will tell.
2. The main thrust of the new AA resort will be the family suites which won't impact most current Pop Century guests directly.
True. There will be some defection from people that want more room or have larger parties but I do not see it cannibalizing the other resorts all that much.
3. Each of the resorts, the new AA and the exising Pop Century, are large enough that they will have their own bus system.
No they aren't at least no more so then the All Stars which share a bus system. Pop and AA combined will be almost identical in size the the three All Stars.
4. I see no connection with the busses and the theme at Pop Century.
The point I was making is that the only draw that Pop has over the All Stars is the bus system. It is better because it is not shared with 2 other resorts. When you remove the bus system from the equation it is on par with the other Value resorts. If Pop ends up sharing a bus route with AA (and there is no precedents showing that it won't) It's big draw is gone. The Nemo and Pirate rooms at CBR have been shown to be a big draw for that resort. If Pops numbers drop off after AA is open then retheming the resort AND the rooms to match AA could become economically viable.