Time will tell! I think a return to the Demonweb Pits certainly fits with Wizards' MO of namechecking and referencing older classics. As for whether or not Lolth is needed or not, it'll depend on how they weigh the importance of drow as iconic villains vs. the importance of moving away from the evil drow monoculture in its entirety - whether it's enough to just add more drow while keeping the originals in play. I couldn't say which way that arithmetic would play out.
Perhaps someone has already mentioned this, but my recollection is that it was hinted in Out of the Abyss that Lolth had engineered the demon incursion to get the demon lords out of the way for some personal plot. That always seemed like a setup for a future adventure (or novel), and I don't believe they resolved it. Or if they did, I missed it.
AD