While SO has been a great resource over the years, a significant concern as I see now is the too rapid churn in many topics like various JS frameworks, android development, etc, where things are moving fast, accepted answers are frequently obsolete and have become misleading or wrong, and I have not come across mechanisms to handle this situation.
Also a fragmentation into multiple subject sites also isn't a great idea IMHO, now for some categories for example you have to think of cross-posting to get maximum responses.
I would like to see more effort in this area. "volatile" tags (like JS) should auto mark popular questions as "stale" after a while and shuffle them back into the question queue so that people can either provide up-to-date answers to affirm that the answers aren't stale and are still relevant
Really excellent point here. I can't even count the number of times I've found answers for Android, that turn out to be already outdated. Limiting answers by a date range via Google search sorta works. But, old answers still sneak in.
That creates another problem where I automatically distrust answers more than 2-3 years old. Even if they turn out to be correct.
Also a fragmentation into multiple subject sites also isn't a great idea IMHO, now for some categories for example you have to think of cross-posting to get maximum responses.