When I read your initial post, the first thing that surfaced in my thoughts was Minecraft. This was followed by Second Life/Opensim, then by most of the online games I play(ed), whereby some of those that create armour, mounts, pets etc get a % of the virtual selling price. Not every component is made in-house. Would it be fair to say that there are similarities? I ask because I was intrigued by your opening post Title.
I personally believe MMO’s will grow in use and blend the borders between those environments currently used by business, where reality is so paramount, they use the full stretch of today’s technology to gain it. That technology, whilst out of reach to the average gamer for now, will soon become a reality. Feeling like you are there, will become so enriched when you realise the avatar beside you, is someone just like you, same goes for the whole team and not a puppet. After all, this is the eventual goal of nearly all MMO developers. I have seen online gaming evolve beyond anyone expectations over the past 2+ decades I have been watching and participating, and yet, there are still so much more immersion to come.
Greater feedback (maybe via a suit to begin with, then sound and air projections working on your body) will enhance the realism, the environment created in a space, (as opposed to a pair of goggles), that give full peripheral vision… then the icing on the cake, smell.