I don't know how your grades translate to the 4.0 GPA scale, so I can't comment on how competitive your application is. That being said, most people who apply to McGill's MSc program don't have a paper or a conference talk, so that plays to your advantage.
What I do know is that very few students are admitted in the Winter term. Although officially you can apply to start in the winter, in practice the physics department doesn't usually admit anyone at that time. I do know of a couple of students who were admitted for the winter term, but they both had extensive contact with the department beforehand and had supervisors that really wanted them as students.
My suggestion to you is to get in contact as soon as possible with profs at McGill who you would like to work with. Explain to them that you've already submitted your application for the winter session. If someone is impressed by your experience and credentials, it will help your chances of being admitted.