This has to be something recent(earliest when they first started work on source 2). There's no way valve would have thought they could pull off an RPG on Source 1
http://www.teamfortress.com/post.php?id=18409
So just a brief recap, they are working on a major update with new maps, cosmetics and a new campaign. According to them it should be out by the end of the year, so expect it to come out late 2020.
And no new Halloween map this year, but...
original story on PC gamer
http://www.pcgamer.com/a-garrys-mod-sequel-is-in-the-works/
So after 10 years it's getting a sequel, not much information on it yet, but they want to do a lot with VR. Hopefully valve is giving them source 2 to work with.
well the bigger map sizes could be great for the games if used properly. and better modding tools would be something the community would love. Maybe porting them over isn't the first thing they have to do right now, but they should probably do it at some point. Especially since it's going to be...