The ohio river valley was theorically under french sovereignty, like most of North America, and a conclusion favorable to France would likely uphold that fact. However, the favorable conclusion would need to be won in Europe as much as in Quebec.
Like it was said, facts on the grounds were not always determinant in treaties, at least facts on *american* grounds. Europe was the critical theater.
So if the Czarina lives on, and France wins the 7 years war, yes, a large part of North America would likely remain french, though the big issue for France, then, is making sure enough french speaking people live in America to uphold the claim.
Realistically, I could see Quebec, Ontario, and some territory south of the great lakes remaining French, which would possibly later on mean a pretty different US-Canadian border in the west. Nova Scotia and Acadia (and Rupert's lands someday) could go to France, but Newfoundland is deeply english at that point.
The remaining questions are, how long until the political situation in France or her colonies allow to increase immigration by loosening up the laws that restricted it to french catholics, and whether or not this would impact the French Revolution. A victory in the 7 years wars likely would delay it significantly, along with any meaningful reforms in New France.
