Hi,
I applied for the extension by paper 3 months ago, but still didn't get anything until now.
My university has an electronic enrollment letter that we can request and download. I'm not sure if your university's personal email system has such an option. But if your current study permit isn't going to expire before your supervisor pays for your tuition, then you could wait for him to pay for it. But if your sp is going to expire before s/he pays for your tuition, then you need to apply now. But there's an option called "Restoration of your status" after you're lost your ID and that you didn't apply for it before it expires.
I applied by paper, but it seems there're some different documents required for online. I suggest you read again the instructions on CIC or ask some of your friends (because I'm also waiting for mine to be approved, but I can't say what I submitted were the accurate ones). Hope that will help ...