More then likely it will be some form of B2P or F2P with a cash shop, and that is why they are not announcing the payment model yet. Because there will be a loud hate against either one of those options as anyone who knows anything about MMO's know that P2P is the cheapest way to get the whole game and know you are not missing out on anything that they are selling in the store for real money.
Sadly MMO developers have become greedy and know that as long as they sell items in their store that equal pay to win, as in STO's starship sales and Neverwinters armor and weapon sales and the locked loot boxes that you need to purchase keys to open they can say...no we don't sell pay to win items in our store we just sell the keys to get you those pay to win items and its a gamble IF you will ever get what you are looking for in locked loot boxes because they all have random items in them, some items are good, some not so good.
They also put in a way to get all of those items just by playing the game but that becomes a grind and if you don't mind grinding in Cryptic's free to play MMO's you can get everything for free, in STO you grind dilithium and sell it for Zen and in Neverwinter you grind astral diamonds and sell that for Zen. Zen is their game currency which equals real money...
So having explained how Cyptic/Perfect World's free to play MMO's work the B2P payment model can work identical to that and I would assume ESO will be one or the other, either B2P with a cash shop or F2P with a cash shop. Not saying I want it to be this way but those are the most popular and profitable ways to market an MMO now days.