Damned Ipad ate my first post, so i'll just say this: 4e dragons solved what were problems for me in 3e of action economy and "stat cloud" monsters, who were tougher than what was in the stat block due to spells and capabilities in said stat block, so I preferred the 4e way of doing them and hope they continue the trend.
I can totally get on board with streamlining. Having to make entire spell lists to use 2e and 3e dragons was
not one of their strong suits.
But 4e's approach failed on two basic metrics for me with regards to the dragons.
First, it ditched the identity of the dragons as conveyed by their magical abilities in 2e/3e. As an example, blue dragons in 4e were dire pikachus -- great with a bolt of lightning in a fight. They weren't the clever illusionists who got their victims lost in the desert while obliterating water supplies that the 2e abilities helped them be for me. The latter is much more interesting to me than the former.
Second, it narrowed their focus to the fight. Since combat is only one part of D&D for me, and I still need rules support for the rest of the game, this made them boring and uninteresting to me. I can imagine using a blue dragon that uses mirages and destroys water in play. A blue dragon that just crackles with lightning doesn't inspire me to do anything with it, really. Got no reason to fight it.
The simplification was a good thing, and I hope 5e keeps it simple. Spell lists are not a thing I want to go back to. I just hope it adds back in those two things that 4e dragons lacked for me -- the thematic abilities that made each color interesting and unique, and a context beyond the 30 minutes it'll take to reduce that sack of XP to 0 HP.
I imagine 5e dragons, like the beholder mentioned in today's Q&A, are going to have a "non-legendary, non-laired" mode they can run on, ("legendary" and "lair" seem like things you can add to a critter), which sounds like it'll be useful for anyone wanting a simpler dragon. I just hope that simple dragon still evokes the unique abilities of the 2e/3e era dragons -- that my black dragons unleash insect plagues and taint wells, that my blue dragons use illusions and eradicate water, that my green dragons have charms and nature manipulation that rival the fey...
Those things are fun gameplay elements for me. I imagine they won't be hard to add if 5e doesn't do it by default (it's likely going to be easy to take those spells and just say, "the dragon can use 'em."), but I'd be pleased to see those abilities in there. Given 5e's general "good ideas from history" vibe, I wouldn't be shocked.
But if 5e gold dragons don't grant luck and 5e white dragons don't control the weather, I'm probably not going to be that enthusiastic about 'em.