All the media hyperbole surrounding the recent Steve Jobs rant about Flash has given HTML5 a boost. Reading various blogs and Apple Fan Boy comments would lead you to believe Flash is dead and we're all going to be out of a job in the next couple of years. This is far from the truth. Already Flash is part of the Open Screen project and there will soon be an AIR runtime released for Android.
Apple don't want to support Flash for various reasons and they will push along with HTML 5 and Objective C apps on their closed software platform. Flash is part of the Open Screen project being adopted by all major mobile phone manufacturers, except one... guess who!? iPhone app development is a tempting prospect but it's current popularity, mainly due to lack of competition, will be eroded in the months to come as the mobile phone giants start to offer their own alternatives. Once this happens, the iPhone will look isolated on its proprietary island as apps able to run on a multitude of devices will begin to dominate the market. However, it will be harder for developers to make money in this open arena. It also remains to be seen if Apple really are turning into the Mobile Microsoft and try to stifle development of open source products and force you to use their OS and apps. Unlikely.
Flash, Flex and AIR are perfectly poised to enter the Open Screen app space, so really, you could stick with what you know. Yet, if you're feeling the cold hand of progress pushing your office chair towards the exit, learn HTML5 by all means, learn Objective C if you dare, but those of you with Flash/Flex or Java experience should learn Android as soon as you can