Frankly, complete rewrites under these circumstances are a cop out. It's an easy but ineffective path. What they should be doing is unit tests, isolating bugs and strictly controlling quality. Common bug reports should be triaged, rather than ignored (it's not uncommon to have a bug, and find a set of posts years old discussing workarounds). All it would take to fix Flex would be the will to do it.

The rewrite will have a whole different bunch of issues, and be similarly problematic. It's not like Flex was a bad apple in a bunch of well engineered Adobe software.