They should increase it 5 ranks every 6 months, and every 6 months release new dungeons, weapons, armor, mobs, challenges etc... and NEVER stop raising the cap, even at 100, keep on going. Every 5 rank cap increase, SE should make it a little easier to get within the last 25 ranks of the current cap. So if the cap is 100, its easier to get up to 75 than it originally was. Then to not negate the older content/dungeons, enforce Level Sync/Cap for those areas. And each cap increase, make those mobs drop new stuff, and maybe even change the challenge of the battle.

I am for this, as this could keep the game growing forever. For Me... FFXI stuck at 75 sucked. I got so bored of doing the same thing over and over for how many years? I actually had to quit the game it was so boring. The way FFXI handled new content, killed the old content. It wasn't just cap increases that killed it, its how it was done.