If you're asking if the village that they are sent from gets nobled?
Then the troops poof and disappear and never reach their destination.
If you're asking what happens if the village they are sent to gets nobled?
They still support the village.
The game doesn't care if the village is owned by a tribemate or an enemy or a neutral or even a barb, it just considers the fact that those troops were sent to defend that village after they arrive, doesn't matter who they are defending it from or who owns it, just that they are going to defend it.
I had a long day so my mind is fuzzy that's why I gave both answers, I can't seem to make enough coherent thoughts right now to judge what the question was 100%.