Some areas do lend themselves to the two-tier system more than others, so I am not sure open-source will continue to gain significant market through tiered payment levels. It works for enterprise offerings but not all open-source projects lend themselves to enterprise.

I think its almost more significant that in a post-piracy age (maybe we're not quite there yet), people seem to be increasingly willing to pay for something when they don't have to. I think open source may start to gain traction on a pay-what-you-want payment model, in the way that some musicians have.