Future Dropbox Visa Stamping in the case of intracompany transfer from Canada to USA

I had a question around my current situation. My Company is transferring me to Canada for 6 months - 1 year. I am currently on H1B in the US with a visa stamped on my passport valid till May 2021. I have a I-140 approved through my employer and they said they will be able to apply for H1 cap exempt again in the future when it is time for me to come back from Canada.
My question is if I would be able to still utilize the drop box option till May 2022, once my employer files a cap exempt H1 in the future. (12 months from date of expiry on my current visa).