I just want to focus on this for a moment.
I think you are giving Wizards a little too much credit here. Let's look at a few things.
1: D&D was going to sell well in the beginning years really no matter what.
2: Who's it's nearest competitor? A 14 year old ruleset made by a company who sells most of it's products through it's own online store which consists of books, dice, tile sets, PDF's, toys, etc... Not to mention the fact that you can get all the game material for free online through the SRD.
Do we really even know if it's reached number 1? If you compare Amazon and store sales then it would be number 1 amongst those but if you look at Paizo's entire franchise through their online store then we don't really know because they aren't going to hand out that information.
We aren't talking blood, sweat, and tears here.
So if D&D was guaranteed to sell well in the beginning years no matter what, then at this point, they haven't truly established themselves, right? So now you want them to branch out into new settings when according to you, they don't know how successful they actually are, right?
Doesn't that seem kind of like the exact model used in 4E?