On the 22nd of April 2015, Justin Tadlock announced on WordPress.org that:
Themes are now required to utilize the Customizer API if the theme has custom theme settings. This means no custom settings screens.
The decision was ultimately made on two fronts (so we are told):
- Having a consistent experience for users
- Standardizing the theme review process
As can be seen from the comments on his post this is quite a controversial decision. One of the issues seems to be that many developers will have to rewrite their themes to remove their theme options page. This is because the statement from Justin says:
Then, 6 months from yesterday, all existing themes submitted to the repository [WordPress.org] fall under this guideline. So, mark your calendars for October 21, 2015
It will be interesting to see hows this all works out.