Assuming you decide on having surgery, Dr. Westerberg will refer you to Dr. Akagami, who is the neurosurgeon he works with. There are a lot of very positive posts on this site about both Drs, and I personally found both of them great.
I saw Dr. Akagami first (via a referal from my family doctor in Ontario), and once I decided to have surgery with him, he referred me to Dr. Westerberg. I know that the wait time to see Dr. Akagami varies according to urgency, my tumor is about the same size as yours and I waited about 2 months to see him from the time of my referral. His surgery waitlist is unfortunately pretty long, I've been on it for 5 months and will likely wait a few more. But again, it depends on the tumor size, location, and symptoms you're having, so it could be less in your case. I'm sure Dr. Westerberg will be able to give you a better idea of the timing.
In general these tumours grow slowly and you've probably had it for a long time, so a bit of waiting should not be an issue.
All the best with your appointment.