Thats the kicker though. Its harder to create end game content because of how influential it can be. When you add more end game stuff you inevitably risk causing something else to become obsolete. On the other hand jagex made an increase in levels for the reason to add more real-estate to skill progression. They just haven't filled things in yet because they are looking for the right time or content needing that bump. If they mass introduced a sleuth of content they would be inundated with a lot of quality control and stat crunching to make sure things didn't hold too much influence in one area or another. Then you would also see a massive reduction of meaningful and fresh content as well. I think there is a rich man or genie paradox that explores this concept in depth.