HN user
I'm sorry if we imply a feature freeze by bumping to 2.0... I'm not where you got that. The plan is to backport any API changes to 1.9 or even 1.10 if we need to make one in 2014.
Because removing all of the special case code paths in jQuery 2.0 will inevitably remove bytes from the library, allow us to use newer browser features with less polyfills, and increase performance for modern browsers. Read the post, we are not "dropping support" - 1.9 is going to be API compatible with 2.0.
It will be very difficult to develop a plugin for 2.0 that won't work on 1.9 - they will be 100% API compatible, and pass the same set of unit tests.
The plan is if we ever release a 2.1 to backport what makes sense to a 1.10 if the oldIE's are still a big enough market share.
I'd also like to point out that this concern only comes into play 2 years from now. We are not intending to drop support for oldIE forever, but we do want to make jQuery smaller and as efficient as possible in the newer browsers, and leaving all the oldIE code in as we progress past these browsers wastes time.
Or prefilter if you need to track global requests.
Vendor specific cssHooks are always executed when defined, allowing you to deal with specifics of implementation in your own code.
How exactly do you handle the "change in spec" case in your code right now?
http://trends.builtwith.com/javascript/jQuery is where we get that statistic from