I recently noted there were some new numbers on the 100,000 feature-quality articles page. In May 2008 (based on a January assessment I believe) there were 2,421 featured articles. Today, based on a February 2009 assessment, there are 2,570. That's a 6% increase -- below the 24% growth rate to 2.7 million total articles. If we assume a similar rate of increase, it would take 62 years to reach the goal of 100,000 articles.
initial = 2570; target = 100000; growth = .06; years = (log(target)-log(initial))/log(1+growth)
If we relax the goal to have 100,000 good or better articles, that will require 24 years at a 16% growth starting with 11,024 "good" articles. Of course, I don't know to what extent the rate of growth is increasing or decreasing.