Well, the thing is, Gordon isn't really much of a character at all is he?
I think that the mute protagonist is one of those "out of time" things. It was fine back in the 90s and early 00s, but game storytelling moved on. I always thought it weird that Valve sort of bragged about Gordon being mute, so "the player could be him", like it was actually some sort of intentional thing, and not just tech/storytelling limitations of the era (which is what I think the real reason was--at least I hope so).
If they do continue HL I do hope they kind of let him go by the wayside at this point. Or at least move on from that mute protagonist thing to give him some personality. He'd be a lot more interesting if he was quoting some esoteric physics, or making other weird nerdy/intellectual comments.