It's more likely to be a cameo or one-off trainer. Still, it would be totally appropriate for such to be against Misty. They should figure out some way of arranging for this kind of thing again.
Generally, when Ash takes on 'serious' trainers, they're fairly generic and in the model of Lance from G/S. In that sense, it will probably be similar, unless they opt for a recurring character from much earlier, which might be unlikely as it wouldn't give the same sense of the region being significant.