Longview is going to 4A? Wow. Kind of strange that the former 13-5A (also called 12-5A) could conceivably get back together in 4A. Marshall, John Tyler (should be 4A if not already since it has <1500 students), Nacogdoches, and if you go further back, Texas High and Pine Tree are already 4A. That leaves just Lufkin and Tyler Lee as 5A schools still, or at least I'm assuming that they are still 5A. Texas High of course would never be forced to travel that far again with the other 4A schools that are closer. Also there are a lot of 4A schools in NE Texas, albeit they are much smaller than Marshall (1800 to 1900), Longview (over 2000 last I heard) are giants in 4A for enrollment compared to other schools in Marshall's district. I suppose if the 3A cutoff moves up that some of those schools would be forced to move down from 4A.
As for the south of Austin region, I had heard people discussing that New Braunfels was going to 5A soon. They had just over 2000 students this year. They are projected to have >2200 in 2010 and almost 3000 in 2016. Canyon is still just under 1800, so that leaves Smithson Valley as the only 5A for now in Comal ISD (NBHS is in NB ISD). The expectation though is that Canyon will be a 5A in the next decade although Comal ISD just added a new high school for students that used to feed into Canyon.