I dont think the incabin air filter could cause the air to come out hot, it might come out slow because its clogged but it would still be cold if everything else is the same.
You might have a leak. The dealer told me that my A/C had a leak back in early winter and that it would cost $400+ to fix it, and when i asked 400bucks, he said oh we have to recharge it. Recharge it?, I bought the BiG Ass can for 26bucks plus taxes and probably used 40% of it if not less and the car is blowing cold air like always, bunch of thieves.
Now, I dont know if what he said was true, but seems to me that a bunch of us have done the a/c charge thing, and many with altimas much younger than mine, since mine is almost 8 years old and this was the first time i had to do it, maybe its just time!