There is usually a short grace period where you can still access some online before getting forced to update. You have about a week, if that.Switch 4.1.0 here, CAN play Splatoon 2 online without any problem (using url filtering with my modem, i think that the famous dns doesn't let you play online)
So i will.be fine at least till splatoon 2 gets updated (or maybe it just updates as I can update games while blocking updates but that was when my 4.1 was the lastest firmware now with 5.0 released it may ask for update)
whatever i still have a new game plus xenoblade 2 waiting for me :9