Well it all depends on the fans. If there is a big enough uproar, then Gonzo might see to a new season. Or someone else could do it. We just need a bit of luck, and a LOT of hope. It's too good to end.
A remake will happen. Considering it was the 5th highest selling manga of 2012, I think it will happen but under a different studio, some of the old cast getting replaced, and a focus on following what happened in the manga. It will probably air sometime next year to celebrate the manga's 10th birthday, last for about a year and a half, cover everything up to the Sky Garden Arc, and continue the story in OVAs.