A game of this magnitude has a long way to go, this is just the beginning. It's starwars and its release was coordinated with the release of ep7, there's still ep 8 and 9 to help keep it in the spotlight. Look at the other nameless games that have been in the top 5 highest grossing for a long time, Imo they will eventually be dethroned by this game for the long run. I'm sure they already have plans for what will be for the next 2 years.
Kinda like the big computer companies, the technology exists years ahead of what is available but they only give it out to the public in small increments to keep the constant flow of money coming in. I'd bet leveling up won't be what changes to keep money coming in, it will be major changes to the type of battles.
But that's just my opinion.