Many universities are having to consider pulling out of Second Life if the owners, Linden Labs, implement their decision to charge educational institutes full rates for using the virtual world (see article in The Chronicle of Higher Education, Academics discuss mass migration from Second Life). Up till now educational users have been able to use SL at a discount rate and as a result there is considerable academic activity there.
Earlier this year the social networking tool Ning decided to make all users pay for the service and this resulted in many networks being forced to find a new free host environment or closing down for good. This is of course one of the risks of using freemium solutions run by commercial players - at some point they may very well decide to charge for the service or raise the rates. It's no real surprise but we seem to think that free will always be free.
Linden Labs would seem to risk losing a considerable and dedicated group of followers if they carry out this price hike. Already some educators are planning to migrate to other virtual worlds but the same questions apply as in the case of Ning. How do you know that the solution you move to will not raise the price later on? Commercial solutions need income to survive and if the free model doesn't meet the profit demands then the price will go up. Solutions like SL cost a lot of money to run and develop so what's so surprising about the company wanting to raise the price?
I suspect that those who are committed to using Second Life and have clear reasons for being there will pay up and continue. Those who are not so dedicated will of course close down or move elsewhere. There are plenty other worlds to inhabit though maybe not as diverse and populated as Second Life.