I'm not sure what they expect...we've all seen it happen with social-media, it starts out all open and free, and then investors get involved and soon enough people have already moved on to the next open and free alternative. 4chan is the only exception to this rule. But if 4chan somehow got transformed into a for-profit service, then things have already gotten very bad.
And I recall in my case there is not a big exodus but people slowly moved over with die-hard fans on both sides.
As a comparison, with 20MM the devs can probably build the new thing, serve media over CDNs and out-SEO reddit with some to spare.
I think moot and hiroyuki did try to monetize 4chan but with mixed success. See the 4chan pass and splitting of the SFW boards into a separate domain.