What to learn for RIA
If you have a year to prepare I recommend that you research all the technologies you can.  Build the hello worlds for the different platforms.  Then build the SAME simple RIA on each candidate framework to get a good feel for the differences.  Obviously you will not uncover every little gotcha, but the gross architectures and styles will be evident.
I am planning to build a RIA about a year from now (when my current contract ends). What technology would you recommend investing time in? 
I will need good cross browser/platform support for video, music, and canvas.
And ideally I would like to leverage my Python skills.
Silverlight looks interesting because I could use Python through .NET. But I'm on Linux so I'd always be a 2nd class citizen. And it has a low install base.
Flash on the other hand has a large install base.
And I'm not sure about JavaFX because of the Oracle deal.
Or should I hold my hopes out for HTML 5?
Thanks!