Popular jquery-rails gem often wait few month before update jQuery, because it contains also UJS adapter and need to test it. For example, there is no jQuery 2 for Rails by jquery-rails.

If you don’t use UJS, try jquery-cdn:

• It always contains latest jQuery
• Uses CDN to server jQuery in production and local copy in development
• Easy to maintain, because gem versions is same, that jQuery inside
• Works with Sinatra and other non-Rails environments with Sprockets
• Has 2 branches: with jQuery 1 (in you support IE 8) and with jQuery 2