Well I hope he is good and enjoys the back benches, maybe he’ll be on “Have I got news for you.”It's not that early to be fair. It is just over half way through the Parliament ( In OTL Blair resigned two years & month or so into the 2005-2010 Parliament). He is giving his successor just over two years if he decides to go for a full Parliament (no OTL Fixed term Parliament Act here). Although there have been rumours of health issues (look at the 2018 General Election, rumours he collapsed after the final debate), he frankly just wants a couple of years on the back benchers before retiring to his Scottish farm, after all he has been in the HOC since 1979, he has been PM since March 2015 and turns 74 the day before he formally hands in his resignation.
I am kidding on the Have I go News For you.