Haven't seen one of these in, what, a record few months? Nothing like a good old 5E wishlist shindig!
Good points, delericho, evidently I must spread XP around first before giving you more. I too don't want to "go back," but also feel that 4E left some important elements behind that I'd like to see (re-)integrated into 5E.
PLAY STYLE: I'd like to see more options for styles of play and the power level of a campaign's starting point. I do not want to go back to 1E-style early levels, especially for magic users, but it would be nice to see some kind of variant system for Novice or Apprentice Tier that facilitates "off the farm" campaigns.
RITUALS/SPELLS/POWERS: I'd like to see the re-integration of rituals into the flow of the 4E game session. In that regard, I'd like to see arcane powers become closer to pre-4E spells. I've grown to enjoy the power system but feel that it needs to be more "invisible" to the play environment so that there aren't just the four roles-as-classes wearing different "clothes," but many different classes with different sub-rules, all based around the power structure but without just being re-fluffings of the same old powers.
MAGIC ITEMS: Magic items need work. I'm not sure what the solution is, but the problem seems to be with too many items having just a daily power; they just don't see magical anymore. In previous editions you'd have magic items that had powers that couldn't be reproduced by player powers; I'd like see more unique powers in magic items (e.g. the old style vorpal weapon).
TIERS/MODULARITY: I love the tier system and would like to see its strengths exploited in greater modularity, perhaps with guidelines for starting campaigns at different tiers; this would work well with the so-called Novice or Apprentice Tier I mentioned above, but maybe also an Immortal tier beyond Epic.
BASIC/ADVANCED: More modularity in general. And this leads me to the biggest change I'd like to see, and it relates to delericho's starter set: I'd like to see a simpler core system, with most rules being optional and "Advanced." That means all classes would be akin to a pre-packaged build with a few choices, but no feats or powers or even skills; if a given campaign or player wants more detail and customization, they can "un-pack" an aspect of their character into feats, powers, skills, talents, etc. But Advanced and Basic characters could work in the same campaign, depending upon what the DM allows and the players want.
COMBAT: In a similar sense, I'd like to see combat that is easier to run without miniatures. As I've said before, I like using miniatures I just don't like having to use them (OK, I don't "have to" but the rules take miniatures for granted). Even more so, I'd like see quicker combat! This has improved, but still...
HOUSE RULES/CUSTOMIZATION: Finally, and perhaps most importantly, I'd like to see more guidelines for creation of classes, magic items, feats, etc...more customization; a feature within Insider that allows the DM to create stuff and just plug it in. This is a huge problem right now - that the canonical tools, even the rule books, don't allow or at least facilitate house rules and DM creations, one of the hallmarks of the D&D experience. I'm sure it isn't easy to program, say, a template for creating magic items into Character Builder, but you've just got to make it happen, WotC.
I'm sure there's more, but I'll leave it there for now.