It won't work.
If XT is adopted, XT wins, there's no other chain, or at least there's no other chain with value.
You may find someone that lived in a cave for the past year and scam them using the abandoned chain, but that's not something you'll want to brag about, I think...
Since the losing chain value doesn't drop to $0 in 0 seconds, there's a chaotic time during which the op's scenario may unfold.