Raiola is his agent, but yeah I wouldn't be surprised if he stayed another season. Plus I'm not sure the demand for him would be high, but a persistent team could get him for good deal this summer anyways, dont think Gladbach has the staying power to convince players to be content to stay if they wanna move. But for his development might be actually smart to stay.
In the bundesliga comeback I enjoy seeing him and Plea playing together, such a fluid partnership.