I've been following this from its announcement last year, so hopefully can answer some of these questions.
First of all, for the record, they have not officially stated a business model yet: http://help.elderscrollsonline.com/app/ ... ss%20model
Personally, I hope for buy-to-play, where you pay for the disc and then can play freely.
The available platforms will be PC, Mac, Xbox One and PS4. PC and Mac can play together, Xbox One and PS4 each have their own servers. (I would hope they may change this to being a Xbone/PS4 combined server, but there's probably too may logistical issues with that.)
I'm sure they have also said, although I can't remember where, that there will be large-group end-game PvE content, they just aren't in the style of traditional
raids. They will be "Adventure Zones", but the devs haven't yet decided how much, if at all, they will be instanced, or what size groups you will be able to form to tackle them. Adventure Zones will be the subject of periodic releases after launch, and may not be in at launch.
in at launch are the Thieves' Guild and the Dark Brotherhood. Hopefully they will turn up later.Tamriel Foundry's FAQ
and the Official ESO Support Site
have more details.