Given a travel related situation, and given a specific question about the situation, summarize the question into a title

I currently living in Canada and I came back after a short visit (3 days) last night from USA. I came through Windsor and I forgot to hand over my I94 to the Canadian officials.

I am currently on work permit here and I'll be visiting us again during Christmas break ... I wanted to know what will happen if I try to re-enter.
The i94 expires in May 2017 so I'll be re-enter in before it's expiry and I'll be traveling through air through Pearson airport in Toronto.

I looked at a few of the websites/forums and they said it might take a month or two to update even if I mail them back. But, ill be re-entering again by that time so I am.not sure if I should mail them.

What should I do now ?
I forgot to return my i94 yesterday and I am planning to revisit USA in December . What will happen when I try to re-entry