It's a good question, one I have pondered myself. I suspect that, were he alive during the period in question, his role as Divine Crusader would mandate opposition. Would he succeed? Obviously not. At best he might delay what we now know to be inevitable.
It's a matter that will likely never be put to the test. As all but those new to the forum likely know, my decrepit avatar is an older gentleman, not of a long-lived race. In all post-Crisis scenarios I've envisioned, his days as a resident of Tamriel are numbered. Prolonged certainly, thanks to the restorative blessings of the Nine inherent to his position as Crusader. But even that has it limits. One such scenario sees him, as his time approaches, abandon Nirn for the dubious benefits of life in the Isles, at long last assuming the mantle of Lord of the Realm. This of course opens the possibility for a return to Nirn, though I question its feasibility. Past a certain point, could he physically set foot on Nirn without crumbling into dust? Who's to say?
The scenario that rings truest sees his remains housed in a sarcophagus at the base of the Dragon Statue within a restored Temple of the One. Such is stipulated in his will. Funds for the purpose are set aside. Sadly, I suspect the grave to be desecrated at some future date. The Empire's new masters might tolerate and even sanction a high profile resting place of the Champion of Cyrodiil, but could they condone such honor for the Nine's representative on Nirn?
Despite the above, it is perfectly acceptable to alter history in our own individual Nirns, including scenarios in which the Aldmeri Dominion never bears fruit.
-Decrepit-