So,what do you think happened at the end?



Here's my theory: The Vortigaunts were working for G-Man.They saved Gordon after he destroyed the Nexus(it's seen as if it's not destroyed but it actually is)and sent him to the future,in a timeline where harm won't come to him and where he can't cause any possible harm.They were in debate with the G-Man for weather Gordon could still aid the Resistance in defeating the Combine or not,'cause G-Man believed he could be dangerous due to his incredible abilities and skills and the fact that he beat the Nihilanth which is considered the leader of the evil side of the Shuulathoi.The debate is also seen in Episode 1's beginning("We'll see about that!").



I believe that should be a possible explanation for a good Closure.