Gmod / Finish

How many years do you think this game has left?

I know 2 years time

It's still doing pretty good according to SteamCharts so I'd say possibly even 5 more years. If Garry makes a second Garry's Mod on Source 2, which I don't think will ever happen, Garry's Mod 1 will plummet pretty quickly because this game and engine is so outdated.