An important discussion on the PHP "internals" development mailing list is taking place. It's one that you should take some note of. It concerns the next step in transitioning PHP applications away from the very old mysql extension and towards adopting the much better mysqli extension or PDO_MYSQL driver for PDO. This would allow the mysql extension to, at some as-yet undetermined time in the future, be removed. Both mysqli and PDO_MYSQL have been around for many years, and have various advantages: http://php.net/manual/en/mysqlinfo.api.choosing.php
The initial RFC for this next step is at https://wiki.php.net/rfc/mysql_deprecation I would expect the RFC to change substantially based on current discussion. The crux of that discussion is the timing of the next step of deprecation. There is also discussion of the carrot approach (showing users the benfits of moving), and stick approach (displaying warnings when the mysql extension is used). As always, there is a lot of guesswork going on as to what MySQL APIs are in current use by PHP applications, how those applications are deployed, and what their upgrade cycle is. This is where you can add your weight to the discussion - and also help by spreading the word to move to mysqli or PDO_MYSQL. An example of such a 'carrot' is the excellent summary at Ulf Wendel's blog: http://blog.ulf-wendel.de/2012/php-mysql-why-to-upgrade-extmysql/
I want to repeat that no time frame for the eventual removal of the mysql extension is set. I expect it to be some years away.