Last time I checked...the next Brit election (unless something occurs) is spring 2020...a LONG way away. I think Corbin will be allowed to play out his gimmick as long as possible, and then in the summer of 2019...some staged fake party coup will occur and bring in some fresh face like Yvette Cooper. At that point, spring 2020...a flip on leadership will occur and the Labor guys return.
Now, how this affects after-BREXIT which will have had two years to develop and take some root, is beyond me.