I would think it’d be higher than 2 million.
They need enough subs to pay for the game’s infrastructure, maintenance, upkeep, and especially development. They’re still churning out content, so they’re still making plenty of money to do so.
Surely this would require more than a piddly 2 million subs. Back during Vanilla when there were only 2 million subs, things were a lot cheaper back then. I doubt the game could survive on 2 million subs TBH.
The reality of it is, people are pulling numbers out from their behinds when they have zero evidence as to how exactly many there are.