1) Get yourself placed on the "Legacy team" that is supposed to "minimally support the application while we transition to the new system".
2) Do whatever the hell you want with the code base (i.e., refactor as much as you want) because nobody cares about the boring legacy system.
3) Respond directly to user/customer needs without having to worry about what upper management wants (because they are distracted by the beautiful green-field rewrite).
4) Retain your job (and probably get a promotion) when they cancel the rewrite.