In the meantime, the English version of FFRK is scheduled to have new events weekly. Given that there's a large pool of events to pull from the Japanese version, it sounds like there's no risk of us running out of new content any time soon. It's also likely that we'll see a different release schedule for events out here, so the order the events were introduced in Japan may not necessarily be representative of how they release in English versions.
The different markets will also influence the characters that we'll see in the West... or at least, the order in which we'll see them. Both the Western and Japanese markets have different favorite characters, so the developers consider this when deciding which characters to introduce and when. That said, our version of the game will release with close to ten characters, and the debut event should be available early on (though we don't yet know which game/character it will focus on). While they want to appeal to the fans and choose characters that will be popular, the balance of the game is also considered. So, for example, we likely won't see the likes of Cloud followed by Squall, Auron, etc, since those are all similar physical-centric characters. So the developers need to introduce a mix of other roles in as well — healers, casters, and so on. All told, the Japanese version currently has 20+ characters so far, so there's no shortage of characters to look forward to.