while HTML 5 will grow in popularity, it will never replace flash.
There flash games but not really HTML 5 games, also while it will be easier to add hardware acceleration to HTML 5, it wont perform as well as flash in terms of quality.
flash has the ability to do an extensive amount of post processing on videos, which is why many flash videos look better than HTML 5 videos.
adobe needs to work on improving hardware acceleration in flash, and even add CUDA and BROOK support so the post processing and all of the other stuff done by flash can also be accelerated.
As stated by adobe, and nvidia and ATI, only certain model cards can support flash acceleration, and all of the cards that support it also support either CUDA or BROOK. current flash with hardware acceleration still has a pretty high CPU usage and thats because the entire process of playing a flash video is not accelerated, just the video file and even then the video data has to be in h.264 this limits what the acceleration in flash by a lot.
they need to have flash use CUDA and BROOK, it should e easy for them as they have a decent team coding flash, and also many open source groups were able to make rainbow table generators that supported CUDA and BROOK, and many video converters are starting to support CUDA, which shows that the GPU processing can be used on a wide range of things.