It means that eventually some site you have working you won't be able to update to the latest version of PHP without it still working. However, php 5 was released over a decade ago, and it is still very easy to find a server that supports PHP 4. Realistically this won't be an issue for you for a decade or more.
We will be updating Data Bridge to work with mySQLi. We will also try to make it as easy as possible to update pages already developed, so that we hope you wouldn't have to start from scratch.