In this thread, I mentioned a system wherein there would simply be formulas governing class progression, so that no max level and no class progression charts would ever need to exist. Just a breakdown of each class in prose form, detailing when you get a new die or bonus.
This method would have multiple benefits, the most obvious being ease of character creation beyond 1st level. Take the level you want to create your character at, plug the level into a few equations, and write the answers down on the character sheet. Easy.
Not having a character progression chart would also remove hard or implied caps to adventuring. Go as high as you want, adventure as long as you want. No more max level to represent an end game.
The problem, of course, would be a certain amount of mechanical stagnation. This could be mitigated by allowing each class to excel beyond the others in a single area, and allowing that divide to grow as the characters level higher and higher. If, for example, a cleric is meant to be a middle-of-the-road melee damage dealer, and a ranger starts out dealing almost double the damage of the cleric, the divide needs to remain consistent, if not become even more pronounced.