I think, in general, S4 would translate to a house much more easily than the other 3 seasons.
Maybe I'm wrong, but with so much of the season actually taking place in the Upside Down, it feels that way. Throw in Vecna and the demobats and I think it would be the best ST house they've done.
As far as the White Whale IPs - is The Last of Us even considered a White Whale at this point? I really want to see it but I'm not sure people have been clamoring for it like Scream/Conjuring/etc.
And I may be wrong here as well, but with The Lost Boys being, for all intents and purposes, a "dead" franchise - I feel like the rights could be relatively easy to get. I know there's a remake coming, so I'm not sure if they'd want to wait for that?