Yes, that's correct. One you release your "M" version, you can delete all the "x.to.N" update files from both your computers and your servers.
Implementation clarification
If I understand your answers to another post I read, then the following is correct:
For a given sequence of updates, 1...N, wyUpdates needs each version to have it's own unique delta to N:1->N, 2->N, 3->N, ... (N-1)->N.
When N becomes M, then a whole new set, from 1...N all have to have a new delta added, to M:1->M, 2->M, 3->M, ..., N->M
Correct?
Good point! Thanks