Asking us to predict the future is hard (and probably a little off-topic). But I'll go ahead and contribute what little knowledge I have...
Per conversations in Craft Slack, a few reputable plugin developers have casually mentioned that they may or may not be working on plugins for the following WYSIWYG editors...
Because Slack conversations are so ephemeral, it's hard to say how much weight these comments truly carry. Multiple people mentioned working on a CKeditor, though it's possible they all stopped because "someone else is working on it". Froala was mentioned, although the cost was certainly an issue. And Tiny MCE was mentioned, although possibly as a joke.
I'd recommend tuning into Craft Slack, where you may be able to get a more up-to-date answer to this question.
(Personally, I'd love to see a P&T version of the CKeditor. But that's like, my opinion.)