That said, I don't think that random guy is an Observer. Why would there need to be more than one of them within the same vicinity?
If I were a betting man (which I am) I would guess that there will indeed be multiple Observers, although initially the other Observers will be portrayed by the same actor and may not appear on-screen at the same time (unless Bad Robot feel like running up their CGI budget). I could be wrong though.
I wont discount the idea of that dude being an Observer..the line of thought has possibilities.