Jquery is one of the building blocks of modern web upon which, many web pages, plugins, functionality is based.
That said I think it would be better for the community if they went a bit slower on major releases like 1.4/1.8/1.9/2.0, and more on minor releases for bug fixes, compatibility and performance improvements.
That's what 1.8.2 is about, and we'll do minor releases as needed.
The reason 1.9/2.0 is happening only about 6 months after 1.8 is that there is a lot of demand for an oldIE-free version for mobile and modern web apps, as opposed to public web sites. It's important for us to line up the APIs in the 1.9/2.0 versions but we had to give people enough notice about deprecated features.
You can expect the pace to slow down after 1.9/2.0 comes out.
There was some discussion about this on an earlier jQuery-update-thread: There's no urgent need to update your sites to the most recent version. Other than with server side software, you have close to no security issues when using an older version.
That's not quite true about security. There is a very bad practice some ajaxy sites have where they select parts of the page using `$(location.hash)` [1]. Since that string is in the URL and entirely in control of outside code, it's pretty easy to get the page to run something that might send information to a third party. That particular hole was closed in jQuery 1.6.4 but there are still plenty of people running older versions.
We're tightening this down even further in 1.9 to prevent a few other cases, which I am sure will break some code, but the only real solution is good input hygiene and HTML escaping on the part of the application itself.
That said I think it would be better for the community if they went a bit slower on major releases like 1.4/1.8/1.9/2.0, and more on minor releases for bug fixes, compatibility and performance improvements.