I sincerely hope that WotC will eventually do a few new settings for 5th edition. They haven't come out with a brand new setting since Eberron and every other setting they still use came out pre millennium, mainly AD&D 2e times.
WotC needs fresh new stuff and while using the Realms is smart as far as it is recognized, people do know it, and it's been their most popular setting for probably 30 years... they are doing this in part because it's the only setting where the novels probably make them money and that's probably the main reason why they are focusing on it first.
I'd wish the Realms would become Forgotten. I'd much rather see Spelljammer, Placescape, Dark Sun, Ravenloft and Eberron personally. All of them are way more interesting than FR.
Interesting, maybe. But appropriate as the baseline generic fantasy setting that new players will expect? None of them are. Further, since any new setting they created would have to be relatively generic, there's no point in recreating the wheel. Most of the above will ultimately be supported in 5e, I believe.
I really do hope we see a brand new setting in the next couple of years. I was not around during the time Eberron came out, but (if I remember correctly) I understand a contest was held and Eberron was voted the best? It seems like a quite popular setting, and so I hope it has been commercially viable for them as well; because I'd like to see a similar kind of contest in the future. Seems like one of the best ways to get really fresh interesting ideas.