I can't think of what could stretch Isshu out.
I think the writers did intend to do an E4 arc in DP but ran out of time. That last bit with Ash imagining himself in Flint's place using Infernape to battle Cynthia was too striking to me.
This time since there are no Contests, they can do Ash's story concisely, give Team Plasma roughly the same screentime Galactic got, and have Ash finish the league and move on.
Unless Isshu gets bogged down with endless filler, there's really not much in this arc that could extend it beyond the length of Kanto or slightly longer.
I think the writers did intend to do an E4 arc in DP but ran out of time. That last bit with Ash imagining himself in Flint's place using Infernape to battle Cynthia was too striking to me.
This time since there are no Contests, they can do Ash's story concisely, give Team Plasma roughly the same screentime Galactic got, and have Ash finish the league and move on.
Unless Isshu gets bogged down with endless filler, there's really not much in this arc that could extend it beyond the length of Kanto or slightly longer.