Apologies I've just spotted this thread, and I visit ENWorld two or three times every day without fail, so I've not read all of the 8 or so previous pages. I have read the OP and a few others on the first page.
I've played D&D in all its PnP editions, I'm an old-ish git.
I didn't know Settlers was a board game, I seem to remember an electronic game of the same name, I think I played it on an Amiga 500 many moons ago.
So Settlers is a board game then... I don't play board games, I can't remember the last time I played a board game, I own absolutely zero board games. I have, to the best of my knowledge never been around somebodies house (since I was in short trousers) to play a board game. I have never heard any one say, an RPG person or anyone, 'I played this really good board game the other day...' Actually... somebody did say that once but it was about a racing game and I was 12 or so- Totopoly?
My point is D&D is a game that evolves alongside other media- it's played via VT, PBP, it's available (in other formats) as a MMORPG, various stand-alone PC & or console games and as a... board game. And probably in many other formats that I can't think of.
Settlers isn't, I don't think.
D&D over the years has staked a claim to all manner of niche and/or (supposedly) mainstream markets, and yet it remains (in the PnP format we're so in love with here) a niche game/hobby- not the films, cartoons, merchandising, cards, minis or t-shirts have changed that. Well certainly not in my world over here in the UK.
To conclude D&D can't be Settlers (or compared to a board game like Settlers), if the single edition format generated (like Settlers, apparently) market domination, or at least enough kudos/sales to keep happy the shareholders et al then... Well they'd have probably done that by now, or at least called a hiatus for x years while the owners basked in the glory and the gold. But that would probably not stand them in good stead as D&Ds competitors would just steam ahead (see Pathfinder and the myriad other games that compete/d for the same market- many of which come in multiple editions).
D&D is bound to evolve because Fantasy Fiction Media (and games in general) evolve all the time- I played board games when I was a kid because there were no computer games, I started playing D&D as a 12 year old becuase it was the most fantastical world (it still is by the way) and different than board games- which my parents played. I played Atari Console/Spectrum/Amiga & finally PC/PS/XBox games (mostly RPGs) because they came along and continued to explore a world that mirrored the one in my imagination (thanks to Tolkien and D&D), but mostly just because they came along, and were different/available.
I now play D&D in the trad. format (around a table) once a week, and via Skype & Maptools with people I have never met and who are based all over the globe (see sig). WOTC, it seems, have at last figured this out.
Do people do this with board games? I don't know actually but I can't think of any.
The rules for D&D get reinvented for all the reasons offered above, and also to mirror the wants/needs/desires of the market- remember all the stuff about 4e being a PnP MMORPG et al, perhaps WOTC had an eye on that market. I play D&D (edition-neutral, as in whatever edition) because it explores that world, new media reinvents and rejuvinates Fantasy Fiction (in new formats), D&D repositions/reinvents itself to sell stuff and stay on the front page, pretty much like everything else.
Except Settlers...
I appreciate the analogy but... it doesn't work for me.