Though we have a rough figure, but wouldn’t it be nice to have statistic to reinforce our thoughts? (Taken from O’Reilly Radar - Programming Language Trend). Anyway, these stats are based on O’Reilly book sales.
I am a believer of C/C++, VB (could last a few more years), PHP and perhaps, Ruby on Rails.
Another way to look at Market Share: Programming Language Trends via Google