JQuery 2.0 Released 13 years ago
The point of separation is simpler jQuery development and reduced file-size for the >= 2.x versions. You will serve two files. You serve 1.9.x to IE 6/7/8 users, and 2.x to everyone else. You save bandwidth. You save money.
Features will be the same. It's OSS folks. It's not like it's ran by a closed-source team at Google who may suddenly pull the plug if it deems the project unpopular. My guess is folks who work in enterprise (where older IE still plagues) will be the big maintainers of 1.9.x.