What does this mean?

In terms of future development of the theme, this will be limited to providing critical fixes and security updates where necessary but there will be no further development on the theme template files. The theme will continue to be physically bundled in the core download for the immediate future but it is envisioned that at some point the theme files will be removed altogether and hopefully be provided as a standalone theme downloaded from the WP theme repo.

How do these changes affect current theme use?

Have no worries, if you currently use the default theme on your site things will continue to work just as before. BP has the provision to check whether bp-default is activated or whether a theme has overloaded bp-default templates to the top level of their theme and will then disable theme compatibility mode.

There is one important change in behaviour to take into account if you are currently using bp-default and you need to revert to another theme for testing you will find the option to select bp-deault has been removed, don’t panic though to ensure you can still change themes and re-select bp-default you will need to add a simple one line piece of code

add_filter( 'bp_do_register_theme_directory', '__return_true' );

Add this line to your bp-custom.php file located in the WP plugins directory ( this file does not exist by default and needs to be manually created and must begin with <?php at the very top of the file.)