I'm something of an obsessive-compulsive when it comes to D&D-- I want the game to feel complete, like nothing is missing or unaccounted for, like it's all thought through.
Sometimes this works for me. Sometimes it compels me to pull at threads and I get a fun, insightful article that gives me (and hopefully you) a greater appreciation for the game, or an interesting new way of handling things. Other times it just causes a lot of trouble and stress for me as suddenly it occurs to me that I overlooked something, and now its absence gnaws at me and leaves me dissatisfied.
This, as a matter of fact, is why I haven't really followed the OSR too closely since my big hiatus. I spent long nights cribbing from every blog post, retroclone, zine, and supplement out there-- and occasionally from the WOTC editions that formed the bulk of my background-- until I lost sight of the simplicity and fun of the game and developed a veritable Frankenstein's monster of house rules, custom classes, and edge cases, every bit as bulky and inaccessible as late-period 3.5 or tax law.
Enter 5th edition. A new D&D, compatible enough to be familiar, or even to reuse old material when necessary, but different enough from TSR!D&D to not allow for direct porting, containing very nearly everything I expect D&D to include in its toolkit, it gave me an opportunity to cast off all the cruft I let myself accumulate-- the cruft I would have had to make a significant effort to stop myself accumulating. It was a breath of fresh air.
There was, during the fall, an expectation that this Elemental Evil/Princes of the Apocalypse campaign they're now preparing to launch would include a supplement, an "Adventurer's Handbook." Whether this was the actual plan and they changed their minds or the whole thing was just misguided speculation isn't for me to know, but either way there's no Adventuer's Handbook planned, either for Elemental Evil or for any future offerings, and there never will be. For the foreseeable future, 5e is just those three books.
Of course there will in all likelihood be new options for Elemental Evil, in all likelihood released through the web (and the monthly Unearthed Arcana column as well, of course.) But the ethos of 5e has so far been very-core focused, so I expect they will not be too many or too sweeping and I also expect they will be treated in a more optional fashion than supplemental rules have been in the past. As such I do not feel the same pressure to keep up with them as I did when I played 3.x and 4e. And furthermore since I feel like I don't have anything vital to my conception of D&D missing, only things I might like, I don't feel the same pressure to incorporate additional options that fell outside of the traditional OSR purview that I felt from about 2011 onwards.
For the first time in a long time, I don't feel like I'm having to extensively kitbash or run the Red Queen's race to get the game I need. Instead, I have everything I need and am being presented with an occasional spate of extras if the mood should strike me.
Now if only I can start feeling ready to accept a little vagueness when I'm worldbuilding...