So, don't update to PHP 7 until you can change stuff? They're deprecating it now, but it's not even going to throw a warning before PHP 6, if you read the post. Deprecation moves slowly, and they won't outright remove it for a another few versions, so even if they do remove it for the hypothetical PHP 7, that'll be fast. (In the several years category of fast). Look how long it took them to remove magic_quotes. They've been telling people not to use that for years and years.

I mean, you can all but to mysqli with %s/mysql/mysqli/g if you wanted to be lazy about it. Most the mysql_ functions have mysqli_ equivalents. (But really you should be using the OO MySQLi at least, preferably PDO anyway).