The code in the dev/php8 branch will be the next release. It will be numbered as version 2.0. It will be released sometime before June 30, 2024.
Version 2.0 is compatible with databases created with older versions. The main "breaking" changes involve search indexing, sorting and current location tracking. You will have to reindex older systems at upgrade, as well as regenerate sortable values. With regards to current location tracking, the configuration for the feature is completely different in 2.0, but the older configuration style is still supported. If you use 1.7 current location tracking it should work as-is in 2.0, but we will recommend that all users update their configuration to the current style. Updating configuration shouldn't take more than a few minutes. Reindexing and regenerating sort values can take anywhere from a few minutes to a few hours, or in extreme conditions even a day, depending upon the size of your system.
We have been using the dev/php8 code for our own projects for some time and have updated dozens of 1.6 and 1.7 systems without issue.
There will also be a PHP 8 compatible version of Pawtucket, also numbered 2.0. This version will be backward compatible with existing themes.
An alternate version of Pawtucket is also being developed, with a view towards making it easier to develop custom themes, and easier to meet increasingly stringent accessibility requirements. This version will not be compatible with old themes.
The backward compatible version of Pawtucket will be released at the same time as the 2.0 version of Providence. The alternate Pawtucket will be released in the second-half of 2024.