This feature is being requested frequently for a couple of years. The most promising reply so far can be found here, where EN says:
"We are currently evaluating the ability to add RTL support to our applications (RTL input at least)" (October 2011).
This is definitely more than just "thank you" but still not enough..
However there is some workaround for RTL, provided that one is ready to use the web client in Chrome (see here), as follows:
1. While in Google Chrome, sign into your web account.
2. Press right-control+shift, and start typing RTL (right-to-left).
3. To get back to English-style LTR press left-control+shift.
BTW There is an add-on for Firefox - Force RTL - which presumably works with FF 3. I tried it (a year ago) with FF 7, just in case, but it didn't work..