Hiya!
I should have used the title as my opening but here goes anyway.
I believe releasing products lightly and slowly is going to cause a lot of people to become extremely critical, angry, and a bit selfish.
Let's think about it for a moment. Let's say you buy the three corebooks and you want to continue from there. Well the next product comes out and it's not something you are interested in. Okay no bother. I will just wait for the next one. Well next one comes out a few months later and it's not something you are interested in. Okay, keep calm and just be patient. Possibly one other product comes out that year! Still not somthing I am interested in. A whole year has gone by and nothing else I am interested in has come out and I am starting to get a bit annoyed. I begin really hanging on every word from Wizards because I am product starved. I hear they are doing great and yet I'm left with only the core three I started with. I hear they are only planning to release maybe two products a year and I'm left feeling like I bought into a product that isn't going to see much support. I hear about an MMO but I don't have time to play it and with what little free time I have, I would rather spend that playing some D&D at the table with my mates. Then I hear about this new Alice in Wonderland setting and I get start to get angry and feel a bit of selfishness come on because I hear they are on a limited release plan and instead of getting a setting I want, they are doing a setting I don't want which leaves me waiting even longer. I start to feel this strong urge to get what "I" want and not care of anyone else gets what they want. By this time I am hanging off a cliff here and I could go at any time. A few web articles come out and while they may put a little taste in my mouth, they are hardly enough to satisfy my hunger. Eventually I may get something two years later but by that time I am probably likely to have packed up and moved on to another system.
Why?
Not trying to be glib here, but...why? I can say that I am sort of in the same camp as you. I was looking forward to being able to plonk down money for a new 5e book "if I wanted to". I haven't paid consistently for any D&D "game product" since 1e was still alive and kicking.
That said, I (we; me and my group) have been happily chugging along with our 1e campaign for 20+ years in various forms (and I've been running it for 34+ years...but with other folks the first decade and a half sans one person who's been with me for almost the whole run).
The 5e core three are, honestly, "the game". Everything after that is gravy. It may be nice to have more choice, but it is hardly required for the game to fourish. I do, however, think they need to find some way to keep it's name popping up in magazines, webzines, websites, forums, blogs, etc...and not in a negative way like "5e is gonna die because of no product!" kinda ways. If some sort of OGL would make 3pp feel better (like their mommy and daddy reassuring them that there are no monsters hiding under the bed), then WotC needs to get on that. Take the current OGL and tweek it a
bit to reflect the new 5e rules and anything else WotC really wants out/in it and let the market take over. Or even a "standard, boilerplate-style" license that someone can download from their site, read it over, adjust and sent back to WotC. WotC could read it, tweek it as they feel they need to, and send it back. If both agree to all the changes...license granted for that product or whatever and off ya go! Although the latter would take a LOT more time, effort and money...
As for your "hunger for new content"... I feel you are going to be disappointed. Personally, I also hunger for new 5e content...but I can wait for stuff to come out. I don't
have to have new stuff to play my game. In fact, since 5e's release, the only 'official' 5e stuff I've played/used has been the first half of the Lost Mines of Phandelver (they never got past Thundertree). The core three books are all we've needed.
One of the great things about 5e is is ability to adapt previous editions to itself. Hell, adapting from "similar games" is dirt simple. I've used an OSRIC adventure, a 1e AD&D adventure, two Labyrinth Lord adventures, and a 3.5e/DCC adventure. All have worked without a hitch, and all done pretty much "on the fly" (re: no hours and hours of converting needed).
Not having "official" 5e stuff does nothing but save my pocketbook from pain and suffering, really. Oh, and maybe it keeps 5e from being mentioned/reviewed a little bit more. But honestly, I think people (you included) need to just sit down, take a deep breath, and relax. Smell the roses, watch the clouds roll by and just enjoy what's in front of you. Yes, we can see the speck on the horizon that is the WotC Books coming towards us and a very slow walking pace. But it still coming. Until they get here, look at what you have...40+ years of D&D content to choose from. Life is too short to spend it harping on stuff you don't have. Look at what you do have and what other's don't. I think you'll appreciate it more (re: appreciate the slower release schedule).
^_^
Paul L. Ming