PHP 7 is a major update to PHP and thanks to the refactoring done to PHP core, it will have major impact to PHP performance and memory consuption. PHP 7 is twice as fast as PHP 5.6 running same real life applications and will use considerably less memory.
myDBR will also benefit of PHP 7, especially on PHP code heavy tasks like Excel exports. In normal myDBR installations the speed of the reports usually depend mostly on report's SQL code, but improvements in PHP code will benefit your installations.
We've been running PHP 7 internally since December, so myDBR is fully PHP 7 compatible.
We are waiting for ionCube to release the PHP 7 compatible. Currently the ionCube PHP 7-compatible encoder / loader is in beta (beta 5 as of this writing). As PHP 7 has major internal changes, the ionCube development does take it's time.
As soon as the final and stable release of the ionCube encoder/loader is available, we'll ship myDBR with the PHP 7 support.
As for the older installations, we will drop PHP 5.1 and 5.2 support (there really is no reason using these old version, PHP 5.2 was relased back in 2006). myDBR will continue to support PHP 5.3 and upwards.
In the meanwhile, it is good the check the ionCube loader version you are running (access mydbr/install/loader.php). If you are running loader pre 5.0, update to the latest version.