#3 CM Punk could get a big payday to return to WWE
WWE is quite aware of the kind of power that CM Punk has over the WWE Universe. They still chant his name during matches that have nothing to do with him. It would make sense that CM Punk is also aware of this. As discussed earlier, there is a lot of wrestling on television and that's not even counting ROH and NJPW.
WWE would want to get ahead of the competition and having CM Punk return to the ring would certainly get people to tune in, whether that would be on WWE Monday Night RAW or WWE SmackDown. Ratings do matter and CM Punk could be introduced as a special attraction similar to Brock Lesnar, The Undertaker, or Bill Goldberg.
WWE has the kind of money and have been more than willing to pop open the checkbook. CM Punk would mean huge buy rates and ratings. Punk could even achieve his dream to main event WrestleMania and there's nothing stopping him from putting that clause in the contract.
While it is still an assumption that both sides would actually meet to talk about a comeback, it's CM Punk that holds all the cards.