There will be someone trying to fix this issue.
But for a while, users feel less motivated on sites that clone the data on StackOverflow. And users cannot easily find sites that doesn't clone those data, and it would be somewhat paradoxical to deal with low quality contents there: a site must firstly live with that, but StackOverflow has shown they will be unwelcome sooner or later, and users always debate about this. It's very likely they all will be forgotten slowly, as the informations on them expire and there are not enough users motivated to maintain them. The final clones that are not down are likely read-only or converted into other formats such as a wiki. The same person or company who runs it may also run another separate QA site, but they must have a different path to be successful and to get enough users.
Existing QA sites that are not exactly the StackOverflow model might have some advantages here. Some new sites will also try to advertise their sites in different ways, such as being specialized, having hired answerers, or being incorporated into another model. Many of them may not work well as a model, but they only work because they distinguish themselves from exact StackOverflow clones. And users can have a higher expectation based on how they did their works.
This will be discussed in other types of sites such as forums, SNSes, chatrooms or even mailing lists, maybe even in the comment area of a news sites, to improve their social cohesion. Specially, someone will claim the things you can get from StackOverflow are not the (as they thought) most useful ability a programmer should have. Though it is irrelevant when StackOverflow exists because it supposedly doesn't hurt to also have StackOverflow no matter what you value the most.
Others may criticize the users on StackOverflow that may try to push their common sense to the industry, and say that we should agree to disagree. Those who don't agree to disagree may think misconceptions exist everywhere, and it doesn't worth to clarify anymore. This might not seemed to be that harmful. But new sites that intended to replace StackOverflow struggle to find why they cannot replicate what was on StackOverflow exactly, and don't realize they must do extra works inventing a different way to encourage some of the users to do the dirty, hard and repetitive jobs.
New sites sometimes might also be considered jokes there. Otherwise, users aggressively want to help a new site, bringing in different ideas about how the site should work, only making it less manageable. As there might be many similar sites, users will also abandon a site that they think not good enough rapidly.
And the possible final results are:
- There might be an already big, prepared site advertising too much about their new things and take the role of StackOverflow. They already had their users, so they wouldn't have the difficulty. It's very likely the will refuse to talk to their users too much as that would be likely the way they would have succeeded.
- It's possible that someone finally worked a way mixing contents from different locations and successfully preserving their quality before someone becoming the new StackOverflow. And StackOverflow would be irrelevant.
- With those problems, the path of being another StackOverflow is effectively blocked for a while. But seeing it as a chance, sites owned by a company with an irrelevant model might all want to also have some QA features. And they may develop faster without StackOverflow. One site may finally grow to a complete StackOverflow, with a lot of
legacy fascinating new features that didn't exist in QA sites.
The pace of software development would not be reduced significantly immediately, as the data won't be lost, and they would remain being useful for a long time. And everything new asked there is still answered by a human. Because the problems described on StackOverflow should be isolated enough, I'd say it won't be too harmful to the overall efficiency if a company just hire more people to deal with those problems as a last resort, if that really becomes a concern. And 8k questions/day still doesn't compare to the total number of developers around the world.
But without a default way solving problems for those who cannot solve problems themselves, ugly workarounds might be more common and potentially might increase the number of bugs a little. Or something on StackOverflow is already ugly workarounds, and people find a way to improve without StackOverflow. Who knows?