correct 
Bulletstorm was silly but great fun, took endless piss out of itself and its competitors/ genre bedfellows. They're a good up and coming developer and Epic are right to push them to the forefront of the operation. Give them a Gears-sized budget and I'm eagerly anticipating the results.
Doubt this will be a 'Gears of war 4' anyway, more likely to be like an Halo ODST game. So just a big add on basically.
Still looking forward to it. 
I'm not sure it'll be a 'big add-on,' but I think you're right thinking along the lines of ODST. I doubt it'll be a numbered sequel anyway. It'll either be Pendulum wars based, Emergence day/ early locust uprising, or a game that concentrates on Zeta squad (Barrick etc, the star of the comics) instead of Delta. Prequel territory probable. Although I'd love a pendulum wars game, will they do a Gears without Locust? Would be interesting and mix it up a little.