It would seem there is some consternation regarding the future of jQuery with respect to outdated (to put it diplomatically) versions of IE. A post on the jQuery blog was added to clarify the new direction: versions 2.x will be for modern browsers and the 1.9x line will still be maintained for compatibility with IE versions less than 9.
I think this is a reasonable decision on the part of the jQuery core team. Why should jQuery going forward be perpetually burdened by the legacy IE albatross? Supporting those browsers isn’t free by any stretch of the imagination. All of the conditionals in the jQuery code to make its API work cross-browser comes at a cost in code size and execution time. The freedom from legacy IE support should make the implementation and testing of new API features and refinements quicker and easier. If feasible, some of these changes can always be back-ported into the 1.9x line.
What is so onerous about using conditional comments to include jQuery 2.x for modern browsers and 1.9x for older browsers, especially if the portions of the API one uses are identical across versions? Users of newer browsers will be able to enjoy a quicker jQuery download and improved execution speeds while legacy compatibility can still be maintained without difficulty. Is this ideal? No; one has Microsoft to “thank” for this problem.
New versions of jQuery do not cause old versions to stop working; jQuery is open source and older versions are still widely distributed. The latest version is now 1.8, but I have written a number of sites which use versions 1.4.2 and 1.7.2 and they are still operational. They probably would benefit from a jQuery version upgrade, but that is something to be decided after proper testing. Granted, it is probable at some point browsers which will become widely deployed will be incompatible with these older versions of jQuery, but such a contingency is remote for the near future.
If one is concerned about the future of jQuery’s legacy support, one can be part of the solution by contributing to the jQuery 1.9x line in the form of code contributions, testing and bug reports. If one is not willing to do so, there are viable alternatives such as MooTools, Prototype and Dojo. I am willing to trust jQuery’s developers on this course; if somehow it proves to be suboptimal, it will not bring about doomsday. Legacy IE’s days are thankfully numbered.