Do we still need jQuery UI in Core?

jQuery is a great framework, but it seems to me that there are many of the things that we looked for in jQuery UI that perhaps we can get cheaper with native HTML5 & polyfills.

The Government of Canada's WET Toolkit has dropped jQuery UI from their collection of tools because it adds too much to page load times. They can get more for less if they build up from HTML5 what they need.

This is probably more a discussion item than anything. However, as Drupal 8 is being built for mobile & html5 it is something that should be considered.