If indeed the idea is to have a Ronda vs. Becky showdown at Mania, this TLC PPV is the perfect time and place for WWE to pull the trigger and get the title off Becky, given they could do so in a way that would keep her protected. The simple fact this is a gimmick match gives them the ideal out since Becky doesn't have to be pinned in order to lose the belt so, for instance, Becky and Charlotte could cancel each other out, giving Asuka the opportunity to climb that ladder and win. Or, vice versa, it could be Becky and Asuka cancelling each other out, giving Charlotte the advantage.
Either way, the fact that we don't have to see the visual of Becky being pinned or forced to submit in order to drop the title is the key factor, which is why I'm pretty sure there will indeed be a title change.
As several fellow members already pointed above, Becky then entering and winning the Rumble in order to challenge Ronda at Mania is the obvious aftermath, however I would add a tlittle caviot: Becky enters the Rumble early, hangs on and it comes down to her and Nia Jax. Have Becky eliminate Nia Jax in order to win the Rumble, thus gettimg her "revenge"...
Meanwhile, should WWE elect to go with Charlotte winning at TLC this Sunday, they could then set up a Wrestlemania rematch from last year, only this time Asuka gets her win back and wins the title at the grandest stage. Not that I would mind Asuka winning at TLC, however I feel her chasing Charlotte is probably the better story to be told, hence the reason I feel Charlotte will end up winning come Sunday.