Mind what people do, not only what they say, for deeds will betray a lie
Re: Where is Grimmjow?
Kubo stated Grimmjow is alive and might make a return in the manga, which is ofcourse still running
Also, there has been no information when the anime will return. I'm guessing next year early summer or so. They're giving the manga some space to advance before going further in animation. One bleach episode takes about 3 manga chapters and they were really close at it, like 6 chapters only or so... Even after a year there's only enough manga chapters again that's good for only (roughly calculated) 20 anime episodes or so...
He's probably dead isn't he?
Though it would be great if he was alive, but with Aizen caught and nonsense like Tsukishima, I don't think he would make another appearance.
However, Kubo may also use this as a foreshadow for a new arc after Kugo Ginjou arc.