The answer must, obviously, include the juxtaposition of the confidence gained from his superb achievements this year, against the formidable task of maintaining that momentum sufficiently to defend his titles & ranking. Will he defend them all? I doubt it. Does he need to do so to have another great year? No. To me, if he can win the FO - and he has an excellent clay court game - and defend another GS title/some ATP titles, it will be an excellent result. With his eye on making history, I think he will be making a huge effort to win the FO & the Olympic title. And he can achieve this if he retains his focus.
His attitude and ability to cope with & indeed thrive on stress/the challenge he is facing will, if he sustains it, be half the battle won. For me, it will be a case of the others taking the win from him when they play him, rather than his squandering it away & I'm not sure there is anyone there with an incisive enough game to do it. At least on current evidence.