You can fancy you're chances of the visa before your semester. What is the exact date of your session? .. Moreover, there is also a "last date" to register for a session and normally this can be upto 2 weeks (mine is 5th January and last date is 16th January). So still if you get the visa on the edge of it, you can manage flying and get yourself registered in time.
PS: Ive done my medical on 18th and I'm hoping for the visa any day now. InshaALLAH