That I think would depend on what investment Disney will have by that point as well as the type of guests.
Epic Universe is going to draw people in that will cater to a different clientele much like Star Wars was intended to be at Disney (although I'm not quite certain that was as successful as we all thought) with having Monsters, having Nintendo, rumored addition to Harry Potter, etc. It's going to draw in people that may or may not also be Disney people.
We'd still split time but we'll have to give more days overall to Universal, likely the same days at WDW still so no additional days at WDW.
Harry Potter drew people to Universal that ordinarily weren't really looking at those parks. The only thing Disney has that is akin to that is Star Wars otherwise it's just rides here and there that already Disney people would go to the parks for.
So it's going to depend. Plus how will the reservation system and
Genie+ shake up into it as time goes on. If people view Disney as a hassle to try and arrange park days and Universal at that time still doesn't have reservation system in place well that might hurt Disney and that was not a factor before.