Can we mention unofficial recreations of unreleased games?

Probably only if whatever recreation you mention is significant enough.

Since recreating footage and screenshots is the result of luck and imagination like what ESCalation is doing with unreleased Counter-Strike maps, I often see ModDB pages of 2 unreleased iterations of Team Fortess 2 (Valve's Team Fortress/Brotherhood of Arms & Invasion) that always seems to always be dead/archived, likely due to ModDB policies on automatically unmaintaining mods based on those 2 iterations, so anyone can recreate screenshots and pre-release videos, similar to how the creator of the Counter-Strike map de_dust cited a Middle-East styled map in screenshots of the former iteration of TF2 as a source of the map in Counter-Strike.

So anyone want to do that, just like ESCalation is doing, and make a ModDB group for this wiki?

I think the idea of recreating content is fine, but it's not up to the creator to decide if its release warrants notability. See for instance, Peter Jackson's recreation of the spider pit scene, or TCM's recreation of London After Midnight.