I don't think we would be getting Jasper if we were to get more Steven Universe rep. She's not that important in the grand scheme of things, isn't overly popular, and she doesn't have the crazy moveset potential to make up for it. I think the most likely third Steven Universe rep is either Lapis or Peridot, the fourth would be Amythyst or Pearl, and the fifth would be Spinel. If they're doing semiclones, they could do Stevonnie or Rose Quartz as well. After that is when Jasper enters the equation, but there's still competition from the unchosen parts of the pairs, Bismuth, and maybe even the Diamonds.
I think it's likely that both series get up to three reps, but I don't think they'll go beyond that. Yes, the game will go on for awhile, but there's such a wide scope that giving so many reps to one series might be wasteful. There's also the problem that Steven Universe is, as far as we know, a dead series. In 4 years time, why add a fourth SU rep (when it hasn't gotten anything new in half a decade) when a new show could get it's forth rep? There's also no way of knowing how long the Gumball revival will go for, it could very well be a small revival mostly for character send-offs (ironically like Steven Universe Future). I hope I'm wrong on both fronts, but I think it best to temper expectations for the time being.