Why wouldn't the audience swing to PS4 like COD?

Thing to remember is that the 360 was the superior RPG console for the first few years of last gen. Not the case this gen.

Preorders aren't real useful in the determination of attach rate, which is what matters here, since all else is not a contest unless equal which it is not. That being said the reasons for last gen barely if at all factor in here. This is not an RPG that comes out first and runs better on one platform, this is an MMO that will come out at the simultaneously with little variance in performance.
On a side note: ESO is worse than SWTOR, so it'll probably flop out of the gate.

I see PS4 selling more copies... It's the current trend of damn near every game currently.

A PS4 port would take over my life...

The big, third party multiplats are more about userbase size than any brand name. This is why we have seen swings on CoD from Gen 7 to Gen 8.

TES will be no different.

that and Mass Effect ran pretty terribly on PS3 and both will have PS4 games in their series.  I don't see why they wouldn't port ME trilogy (all DLC this time and the elevators and frame drops in 1 and 2 would be a thing of the past!) and Skyrim (all DLC, no framrate dropping more and more the further into a save you got, no long load times especially for the dungeons, no slowdown during dragons and weather, just a really smooth game with possible increase in resolution and draw distance).  Both would be worth $50 in my opinion like TLoU remastered.

i think the ps4 version just has too much competion with better mmos

I thought elder scrolls online went free to play?

There's no subscription now but you still have to buy the game.

TES will sell better on PS4 just like every other third party game and it is an RPG as those games always sell better on PS.