rubygems team has plan to migrate bundler into rubygems at rubygems 3.0. ref. https://github.com/rubygems/rubygems/issues/1681 In current status, rubygems only use Bundler module on test suites. But we should track rubygems upstream step by step. I propose to bundle bundler for stdlib as default gem on ruby core repository. but we have some consideration. such as bundler uses rspec for test suites