Not possible. The population numbers wouldn't allow for a Huguenot France to be set up. 15% of the total population is the absolute highest amount of protestants in France during the Wars of Religion. They couldn't force their views on the other 85%. Its just not possible.
Highly difficult--perhaps even prohibitively so. But then, in Austria, 20% of country managed to do just that to 80%, so I wouldn't rule it out completely. (Though France obviously would pose astounding difficulties.)
However, the question wasn't "can we have a Huguenot France?" --it was "what if the Huguenots win the Wars of Religion?"
My answer--it probably goes very much like what happened IOTL at first, with the Huguenots getting their toleration, only this time the King's a Protestant too. This means they're less likely to cause problems that result in the Kings and their Regents getting on their big Huguenot squashing boots. The problem is whatever happened to exhaust the Catholics enough so that they'd consent to be ruled by a Protestant is likely to wear off in time, so now THEY'RE the ones causing the problems.
So, end result of a Huguenot victory--another War of Religion in 10-15 years. Repeat until the Bourbons are overthrown, or almost all Catholics get tired of the hassle. Whichever comes first.