In theory yes, at least this was my initial expectation.
My recent experience however tend to make me think that Asian languages may be handled differently (maybe due to some specifities on the keyboard?).
I also started with Win8.1 to play with such options.
Today on my office PC I still see a load of languages available. I probably could turn the PC GUI in any language (including Hawaiian ) BUT the keyboard support is missing for some languages.
I can only find IME for Chinese, Japanese,… but this is simply not the same nor enough. It makes me think that those languages are handled differently.
Probably that Emdoor is the most capable to answer this question (but will need to be convey by team next week).