#3 Daniel Bryan
Daniel Bryan is unarguably the biggest superstar of the modern era and it broke many hearts when he announced his retirement in 2016. But, that does not mean that we won't see Daniel Bryan wrestle again.
Bryan has made his intentions clear that he wants to wrestle again and he has toured almost the whole of the USA for medical clearance from various institutes. But, given WWE's past history with concussion-related problems, it is almost a foregone conclusion that he will never be cleared to wrestle again for the company.
But, with Bryan hell-bent on wrestling again and NJPW looking to expand its base in the US, it is very likely that if he decides to Wrestle again, it could very well be inside an NJPW ring.