CIG sent out an email reminder that fight for Pyro rewards will be ending soon:
https://mailchi.mp/cloudimperiumgames/supply-or-die-lc-a-3182025

Currently you can still earn the "Ripper smg" as well as the resupply event rewards (hangar decoration, shotgun with skin, and some ship skins).

I'm not sure when 4.1 is planned to be released. I would expect it to drop before the end of this month.