Well the whole reasoning behind the removal of flash and a choice over html5 is thanks to lobbying companies who want their codecs which need licenses fees to be paid to them for websites to use their software. Flash in itself was designed in a way that it allowed far more flexibility and greater control of the coder. Meaning you didn't really need these license fees.
Due to this is has also been plagued over the years with leaks and weaknesses in the code. My personal opinion is that adobe simply caved under the pressure to remove it and no longer support it, this also benifits them where they force people to use their new software programs.
In most all aspects html5 is the same as flash other then the lack of action script, which allowed way more freedom to creators. But I don't think anyone is going to have a choice, since all the "big" names in the industry and the license holder of flash all going to stop supporting it. They also very unlikely to release the source code. There are some open source and programming groups trying to continue flash and flash websites, but without the source code they have a long road ahead. I also think a lot of web history will be lost due to this removal, many flash based applications simply won't be accessable anymore to the general public.
So wanting or not wanting, we all going to have to accept that flash is probably no longer going to be a thing end of this year.
I have been migrating all my flash apps I build over the years to HTML5, unfortunatly due to how HTML5 works some of the apps I used won't be returning. I completed this work a while ago so anyone visiting my places should be ok in the future.