Well, technically, there's not a mandated, defined "east/west" split right now in 4A, except for the way they bracket the playoffs. There are eight districts, with four generally on the east side bracketed together and four generally on the west side bracketed together, so the two teams coming out of that bracket play in the championship. It's all a matter of how they bracket the districts, though.
So if Southeast Polk or Indianola or Mason City or whomever happens to be placed in one of the "east" brackets, their playoff destiny goes with the east-side squads. It doesn't end the West/East title game tradition just because that school was traditionally West and now it's in an East bracket - the general playoff setup with the champion of the four West districts taking on the champion of the four East districts is the same as ever. In this case, whichever central Iowa team got put into an "eastern" district would now be considered an "east" team (although it would seem really weird to see Southeast Polk, for example, facing Valley in the championship game. Still technically West vs. East, but certainly not what we've been used to for the past couple of decades).
On the other hand, there's nothing stopping the state from changing the brackets so that, perhaps, four districts in the north part of the state are bracketed separately from four districts in the south part. I don't see them doing it, as the east/west thing sort of works okay geographically, but they could. (In 2014-15, when the state didn't set playoff matchups until after the previous round was completed, they could have really mixed things up, but they didn't do it then and I doubt they'd do it now.)
