Webform needs an 8.x version.
Work through Drupal core changes, file issues against the webform 8.x branch and knock off one issue at a time.
The port will utilise D8 design patterns wherever possible (e.g. move webform components to core plugins). Fundamental webform concepts (like using custom components rather than core field types to define form elements) are likely to remain in place due to their ability to scale (i.e. webforms with 100's of fields, sites with 10,000's webforms nodes, webforms with 100,000's of submissions). We will be exploring field based alternatives as resources/time allow, if it's a problem you'd like to tackle please sing out!
Alternatively a lot of great work has gone into the core contact module in D8. For simple use cases it may well fulfil your needs, especially coupled with the contact_storage module. Webform will continue to support more complex form use cases in addition to scaling those forms.
Also see a comparison of form building modules.
Lots! We're only in the early stages of the port and right now we're focusing on feature parity with the 7.x-4.x branch to help us get a working 8.x version. Any help in the process would be greatly appreciated. Interested in learning D8? Please dive in!
Keep an eye on this issue for general progress updates.
User interface changes
Minimal, we're aiming for feature parity with webform-7.x-4.x.
Numerous, we're aiming for feature parity with webform-7.x-4.x while utilising D8 design patterns wherever possible.
Original report by @CarlHinton
Will there be a Drupal 8 version of webforms?