I imagine nothing else will be worked on by id besides doom until late 2015 or 2016. Because they havent outsourced Quake like they did last time. Mb after doom we could see something.
I feel as if ut will be the first of the trio released (ut, reflex, reborn). Then most likely reflex and reborn in last. I feel whoever can come in swiftly with the best product will be able to captivate the entire arena player base (which at this point, let's be real... Is waiting for a new game, doesn't matter which game u come from).
I don't think one arena shooter will ever have the majority share of the playerbase ever again. Quake did, but it's blown its chance now. With so many new things happening from so many different devs new players have many options to find their perfect game.