Is there any possibilities that apple will add the custom equalizer feature on iphones? Because im so obsessed with bass and the BASS BOOSTER isn't enough for me.

There is a non-zero probability that they will do so at some time in the future. How likely that is, no one here can say as speculation is prohibited by the Apple Support Communities Terms of Use.

Let Apple know what you'd like to see here:

Product Feedback - Apple

And, remember, you only get one set of ears to last you're entire life.