I 100% agree with more rules systems to deal with non-combat situations, but where are you seeing this in older editions? All I see is some spells with uses to obviate/bypass some non-combat situations, but I may be missing something; what do you see?
Speaking just for myself, I'd like to see exploration rules focused on (1) how long it takes to explore an area (whether dungeon or wilderness), (2) the likelihood of being detected while exploring and (3) ways for organized communities of monsters respond to intruders.
Obviously, these would all be DM guidelines and not "rules" in the sense of "spell X has effect Y." Likewise, it would be foolish for DMs to track time slavishly when it doesn't matter. But at the same time, good "typical case guidelines" are extremely helpful to new DMs and for setting expectations for groups that haven't played together.
These rules are important to allow players to intelligent tradeoffs about whether they should take the time to search carefully or hurry along before they are detected. And -- since there is a heavy subjective element -- they are the type of rules that are served well by playtesting over a long period of time.
Other types of rules for which playtesting would be helpful:
* Investigation Rules - divination / detection spells, truth magic, knowledge / research / gather information checks, and related feats etc. Different groups will have different desires from the information gathering mechanics. For some groups, divination and character checks is how the PCs are supposed to solve mysteries. In other groups, "mechanical" mystery solving spoils the fun. D&DN should provide a dial. Personally, I'd like to see a GUMSHOE-style skill module.
* Social Interaction Rules - charms and related magic, social skills and class abilities. In the same way, some groups want detailed mechanics for persuasion while other groups want "light mechanics" to provide character differentiation in roleplaying. Other groups want some social magic and little else in the way of rules. WotC should present the range of options, so folks can test what they want.
* Extended Checks - I'm not a big fan of 4e skill challenges, but I think there is a lot of merit to the idea that some non-combat challenges should involve a number of skill checks. This needed much more testing in 4e than it received, and I'd like to see the designers ideas on these rules early enough to go through multiple revisions.
-KS