They do not ask this of everyone. My guess is that this probably means that they expect you to be close to the cutoff. Given your 3.63 for your junior year, this does not surprise me.
If your grades in your current semester are excellent, then this is probably a good sign (but I would not bet your future on it).
I have known several people who were accepted to McGill based solely on their grades from the second and third year of high school. All were at a level where McGill was essentially a safety. Way back when I was in high school I also knew a few people for whom McGill did ask for their mid term grades. They were closer to the cutoff. If I remember this correctly (it has been a while) several of them did get accepted after sending in what were for them very good grades for the first semester of their senior year.
As others have said what the cutoff will be this year may vary. I think that you will have to just wait and see what happens.
Do expect McGill to be academically challenging if you end up attending. Plan to work hard and make a strong effort to stay ahead in your classes.