In totally agree with your assessment that for the Japanese, Korean, (English influenced) and Spanish, French, Italian, and Dutch (Western Euro countries) native language usage all grew at a lesser rate than the 'other languages'. The fact that the others nearly doubled has a lot to do with the GUI availability of non-Roman scripts (for me, read here: Simplified Mandarin). More and more, users have a one-on-one/ small clique interaction when using the internet; be it work or pleasure, and they "want to/ demand" the use of their own script to do it.
It also didn't hurt that "English" speaking "Al Gore" invented the internet/ TCPIP protocol.
(Can't help getting that last one in; there are a few guys at Dartmouth College (U.S.A.)that still get a kick/ ulcer when they hear it!!)