One of the things I find interesting is that somewhat organic/bottoms-up solutions have generally won out in collaboration. Video sort of just naturally grew out of IP-based telephony. (ADDED: And, as you say, video with a big premium attached--much less special conference rooms etc.--was a real niche. But video that was just a part of cheaper IP-based telephony really took off.) Collaborative doc editing sort of naturally grew out of the migration of office suites to SaaS. Chat has been around forever but assumed a more important role.
None of this looks like a grand unified collaborative toolset like a lot of people were thinking in terms of through the 2000s.
None of this looks like a grand unified collaborative toolset like a lot of people were thinking in terms of through the 2000s.