sedges: "Competition for campsites at Trails End and for day use motor permits will be fierce. If you get a campsite reserved , but fail to get a motor permit you do have another option."
Day motor permits for Sag are actually pretty easy to get. It’s nothing like Moose>Basswood. There are a LOT of permits available most days. These permits aren’t tied to a specific day when reserving, but rather to a 7-day period. So if you’re going to be there for a week and you want to fish 3 days, you get 3 permits for that week and then you can decide which days you want to use them based on weather or other factors. You do need to decide by the day before you intend to use, I think— and you will need to drive over to Seagull or maybe voyageur to get each permit.
The overnight motor permits are a different story, those go much more quickly.
To answer the op’s question, the permits become available the same day as the rest of bwca permits, which I think is the first Wednesday in January. If you are online sometime that morning you shouldn’t have any issue getting your Sag DM permits.