Not a surprise as well. Last month on comp.lang.ada I observed that all the top 20 (and 21) languages are now considered main stream - by TIOBE's very own rules. That defeated the object and something had to change and did change - but what?
While the percentage was slashed the relative position of Ada is gone up by one place to 23. But that is still not the top 20 and behind "ActionScript", "ColdFusion" and "Logo".
And a mystery has been solved: Why Lua is so successful! It's the scripting Language used to write World of Warcraft add-ons - We can't beat that! No joking here: The index is about how often a programming language is mentioned in a forum, blog etc. pp. and there a 8.5 million active players looking for a way to pep up there favorite game. If there are at all successful in writing an add-on is a different story.