What kind of how?
How does France keep Louisiana, or how does France keeping Louisiana make expulsion more likely?
- PoD for the first would be that instead of trading Guadalupe back for the territory between the Appalachians and Mississippi, Britain keeps Guadalupe.
My understanding is that as of 1763 in OTL, Britain had occupied Quebec and Montreal, and south of the Great Lakes it occupied parts of current day Ohio, but by no means had they occupied any territory in the Mississippi Valley portion of New France.
- If France had kept Louisiana, which pre-1763 included areas east of the big river as well as west, an expulsion of the Quebecois would have been more likely because of British and colonial fear that the French populace would find succor from nearby French territory, and threaten to undermine the British grip.
-----
If your PoD is expelling the French right after the treaty of 1763, then the French have only Caribbean locales like Haiti, Guyana or Guadalupe to run to. Not much use for lots of white people there. So then there's moving back to France.
They only get to move to New Orleans if the Spaniards are sweethearts and let them into that territory, which they now own.