I'd say it depends on McGregor. Part of what made GSP and Anderson draws is that they were in title fights non-stop and kept winning. The same will be true of Rousey considering how much better than her competition she is.
Will Conor be able to be a long reigning champ or will Aldo and/or Frankie Edgar prove to be too much? If he loses and has to go back to #1 contender and less type fights, his drawing power will take a big hit. People really only want to see title fights or rare draw vs. draw (Anderson vs. Diaz for example), so you have to be a champ to draw as the PPV numbers of guys like Rashad and Chael when they weren't in title fights would show.
If Conor is a long reigning champ, I'd say the UFC is in a better place. Rousey and McGregor are already flirting with 1M PPV buys, and I'm not sure Rousey in particular has even hit her ceiling yet. Anderson needed the absolute perfect matchups (Chael selling the fight like crazy, rematch vs. Weidman with Rousey-Tate coming off TUF in co-main) to hit those kind of numbers. I don't think I'd put Anderson's drawing power in with the other 3 because they have shown they can draw with far less than perfect foes opposite them, which he never really did.
Considering their youth (and the total lack of damage Rousey takes), Rousey and McGregor likely to be more active than the older GSP and Anderson were too, which is no small consideration. Might be an extra BIG PPV or two a year thrown in there just due to activity.