I guess people will lose their minds once Tarquin appears in BG3, either by being an actual NPC or as a cameo.
For those who are unaware, Tarquin is a highly skilled Necromancer and a Scholar in DOS2 who at the end of the game drops a massive exposition about Baldur's Gate, by first referencing a mysterious language known as "Gustavschen", which at the time was a code name for Baldur's Gate 3. And then also mentioning beings that ride dragons and beings that consume minds. And apparently Rivellon no longer holds anything challenging for him, so he vanishes from the world in the epilogue, thus confirming that he actually did manage to enter Faerun

I totally expect to see him in Baldur's Gate.