Given that PLoS is only 8 years old, I think it's too soon to draw any meaningful conclusions from the fact that the open access movement "has failed to displace the monopolists". I think more important is that the trends are moving in the right direction: some high profile journals (like PNAS) have an open access publishing option, and it's unusual for new journals (at least in biology) not to be open access [1][2]. We aren't where we could be 20 years into the World Wide Web, but we're getting there.

[1] http://www.hhmi.org/news/20110627.html [2] http://www.eurekalert.org/pub_releases/2011-06/gsoa-gln06211...