Some will say “but Canadian sellers don’t need to meet the Top Rated Plus standard, being Global Top Rated is good enough for both .ca and .com and Global Top Rated sellers are not required to offer free returns”. That would be a true statement today but what about post June 01, 2018 and beyond? I think the odds are heavily in favour of the same free returns policy coming to .ca and once it does those not willing to comply will become Standard Rated sellers
Anything is possible but top rated sellers on .com have been required to upload their tracking numbers within their handling time in order to keep their trs status for a few years now. That is still not required for Canadian sellers. So far they realize that it is very difficult for Canadians to meet exactly the same standards as US sellers. It's possible that will change but there has been no indication that it will change so why spend time wondering it will?
You're mistaken in that US TRS who do not offer free returns will lose their TRS status. They will remain TRS as long as they meet other required standards. Free returns will be required for a listing to have the TRS plus badge and to qualify for the discount, they are not required for a seller to be TRS. There is no such thing as a TRS plus seller, there are only listings that qualify for the TRSplus badge and discount. A seller can be TRS but choose not to offer the trs plus on their listings so they wouldn't receive the discount. Or a seller could choose just to follow the plus requirements on some of their listings.
Right now there are US trs sellers who don't have the badge because they don't offer returns or they have 1 day handling. There are also some Canadian sellers who have US trs status...I did until recently. I didn't have the badge because I didn't all of the tracking requirements but I was still trs in the US and if you or other Canadians have that status in the US now, that won't change in June.