I'm new so I may be missing something here, but why is 2015 a good year for the Source engine? Aside from some animation an audio updates for CSGO, as far as I can tell there really hasn't been anything super significant happening in terms of new Source games or mods?
I should say that I don't think the CSGO levels people make are unimportant or insignificant, but as far as the engine goes, or how Source is perceived outside of modding communities, nothing big has happened.