You don't always need to "just go up one caliber"... The reason the AI is, and will always be relevant, is because it is all about getting the absolute most effeciency out of a standardized caliber's case. By adding that extra 5-10gr of powder capacity, you have just unlocked potential not available in the standard SAAMI configuration. That slight edge can sometimes be the difference in a 1000 yard shot, and an 1100 yard shot. So, you just have to sit back and figure out your priorities. I like tinkering with things and getting the most out of it that I possibly can...So, I love the Ackley Improved calibers. Plus, I honestly feel the AI case designs with the minimal body taper and the 40* shoulder angle is a much more efficient cartridge design.
Once you master case-forming for AI's and you start getting into wildcatting and designing your own, it can be highly addictive. Especially if you're really good at it. Not braggin, of course...