If you're referring to a deadline and you're wondering if you will have a class in time, then yes. This is a correct sentence.

If you're worried that your class might begin late (for instance, if it's almost time for class but the teacher has not arrived yet), you should say, "Will we have class on time?" This is probably the meaning you intend. If you're worried that your class won't happen until after a particular deadline, then your sentence is fine, as Daniel says. This would be a more unusual sentence, though. We use "on time" to describe something that occurs at the correct time. A bus is "on time" if it arrives at the time when it is scheduled to arrive. Your class is "on time" if it happens at the normal or proper time. (If your class was supposed to start at 3:00, but instead it started at 3:15, it did not start on time. It started late.) We use "in time" to describe something that happens before a deadline, or before it is "too late" for it to be useful. If you arrive at the airport "in time," that means your plane hasn't left yet. You're not too late to catch your plane. We usually use the longer phrases "in time for" or "in time to," and describe what wasn't missed. "I woke up in time for breakfast" means that I did not miss breakfast. You can use just the phrase "in time" in cases where it's obvious what the consequences would be if you missed the deadline (for instance, when you say "I got to the bus stop in time," it's obvious that you must be talking about getting there "in time" to catch the bus). You could say "I did not get to class ON time, but I still arrived IN time to take the test." This means that you arrived late, but not *too* late for the teacher to let you take the test.