Unfortunately I doubt it's still going to stop being prevalent for several years after that. At least maybe some major sites will stop using it right away, but it's not like flash will stop working and people will stop using it.
The benefits of HTML5 over flash essentially boil down to faster performance, less resource intensive, less pages crashes, Flash constantly has security issuess, and HTML 5 is cross platform inherently and built into any mildly modern browser. Also back in the day Jobs always said Flash was the number one reason Macs crashed. I don't know the accuracy of the statement any more, but I'm sure it's still a solid reason. I believe insecurity is a major reason most companies have been pushing against it the last few years. Random Gizmodo article:
http://gizmodo.com/disable-flash-1688209571
I also would say good luck to only having Safari on your computer. There's always the stupid government/healthcare/utility provider/absolutely necessary site that is just completely un-functional in Safari.