Please remove if I'm breaking any rules, but Blizzard is upgrading all WoW accounts that ever had a license attached to it to Shadowlands. You don't even need an active sub.
https://www.wowhead.com/news/return-...ber-5th-328466
I know SL would have been added to the base game before the DF launch anyway, but you can get it a couple of months early I guess.