Ash traveling with two girls could easily happen. Ash traveling with just the two girls, not so much.
I'm waiting for Ash to actually travel with some of the recurring past-cast and some new ones. Could be interesting to see a past Rival join his team, a current traveling companion stay, and a new person. The most interesting combo of that for me? Gary, Iris, and new girl from B2/W2. Reasoning:
-Gary's been self-sufficient, self-righteous, and stuck-up before, but grew into maturity as more of an actual friend to Ash. Plus, he's well-established despite the low appearance rate.
-Iris bemoans how much of a kid Ash is, despite acting like more of a kid than Ash at times. Also, we've seen very little from her in regards to her Pokemon (i.e. does she actually have more than we've seen her travel with back at home).
-New girl would be a fresh face and potentially a fresh personality archetype. We'd get the rare two-female-companion situation, too.