No no no no NO. It's time to get rid of Flash. Open-sourcing will make it live forever. Flash has very little to offer that is not at this point duplicated (or improved upon) by others. It's also woefully insecure. "Many eyes make all bugs shallow" will only work for the most trivial bugs in the most common code paths. Plenty of vulnerabilities will remain. In open source, they'll be even easier for attackers to find…
Very narrow minded. Tens of thousands of games rely on flash, along with many movies and general history of the internet. Open souring it will preserve countless hours of lost work.
(Hello downvotes? It's true, we preserve all of those things through virtual machines of one variety or another. The Flash plugin doesn't magically stop working because Adobe stops developing it.)