Virtual worlds - waiting for take off

I attended an interesting seminar in Second Life yesterday. I've been to quite a lot of events there over the last year or two and still find it fascinating to see my avatar sitting with other avatars participating in a meeting while I sit at my RL desk drinking coffee. This one was about how business and the academic world in Norway were using SL and it struck me that SL seems to have reached a plateau after the explosive development of 2007. Plenty of companies, universities and other institutions working in there but it's still in its infancy really. When will virtual worlds become mainstream?
It's still a bit too exclusive. SL in particular requires client software, regular updates and most importantly a really good graphics card. I've already had 2 computers who couldn't cope with SL and several people I know have given up with SL when their computers started struggling. There are now several new virtual worlds on the market (Google's Lively, Vivaty and 3DXplorer) but all seem to have drawbacks and none are as massive and immersive as SL. The new ones work in your browser and are integrated to the web (great!) but restrict communication to text chat and have only pre-set environments (game set and match to SL).
Businesses in SL are testing the technology and waiting for a mass market which doesn't seem to be happening as fast as we had hoped for last year. Waiting for the killer application takes time and when it comes it's not often what you expected.
Look at SMS. Originally it was a rather basic and dull signalling function in GSM phones to enable operators to tell you that you had a voice mail message. It's not even so simple to use since you have to text everything on a tiny keypad with multiple clicks. The developers could never have imagined that SMS would take off the way it did and even today, when mobiles have every function under the sun, people still text SMS messages like never before.
Virtual worlds need to be linked to each other with servers all over the world as with the web. You create your avatar and can teleport to any other world. You need to have free, open worlds where anyone can meet anyone and anything can happen and you need other worlds where special rules apply and with restricted access and privacy (as on the web). Just now it's all rather fragmented and mainly for enthusiasts. But I'm probably just too impatient.