I expect there will be large modifications to the hero system far into the future, but we will try to support old heroes.
Heroes receive less skill points at higher hero levels. 2 is the minimum amount that can be gained and there isn't a way to change this. I know it's not great, there have been many requests for a solid 5 skill points per level. The reason for the diminishing returns is to help prevent high level heroes from becoming too powerful and to decrease hero level differences in multiplayer. That's definitely not optimal though. Instead, the game needs a much better and more comprehensive handicapping function which is applied by default (and hence the function would become a standard part of the game). The current handicapping option doesn't work well because army setup points don't translate to hero level differences. Too much ASP allows lower level heroes to rush at game start and too few means that higher level heroes survive to regain all of their value. However, the army which was purchased at game start doesn't come back, so it's simply a matter of time as to when the lower level hero loses. There isn't an ASP value that works, and hence handicapping doesn't work well (and that's also the reason why it's a separate rule instead of a standard part of the game).