Thanks for your message. Yes, this is on our roadmap for 2016.
Can you please have a look at the "Remarks" section of the following page, and tell me which aspect(s) of the "RightToLeft" feature you need with highest priority
(is it the ability to have the column "0" of a Grid be the rightmost column, is it the ability to flip a TextBox horizontally, etc.)?https://msdn.microsoft.com/en-us/library/windows/apps/windows.ui.xaml.frameworkelement.flowdirection