Macros are one of the key things that allow complex raiding and PvP. They're essential for maximizing DPS and for preparing for those specific situations in PvE and PvP. It's rare that a top player will come along that doesn't have a complicated set of macros.
That said, the system is relatively old, and hasn't been given much love in recent years. While new commands are added now and then, the system itself screams
of 2004. There's been lots of advances in not only the way we play the game, but in how players could program the macro functions themselves. Upgrading this system is a topic often discussed, and apparently it's on the minds of Blizzard as well. Taepsilum chimes in:
Devs are looking into revamping the whole macro system at some point, meanwhile, simply increasing the number of slots would probably be good enough. They were having some discussions about doing just that but we still don't have any concrete plans on the way, if anything changes we'll let you know.
Don't hold out your hopes for it happening anytime soon, but if you're like me, you're keeping your fingers crossed for the next expansion.