The Grand High Poo-Bahs of the GOPe only have to keep Trump, or Cruz for that matter, from winning 8 majorities in the primaries to have their way with it. They wrote the rules to get the junior Bush. Even if Trump gets the 8 majorities they will likely try some other shenanigans like producing rules that were put in place but not announced.
If the GOPe try any shenanigans to cheat Trump out of a fairly earned nomination, he will be within his rights to consider the “no independent run” agreement to be null and void.