I wonder if the OGL could solve this issue. The problem is, we don't want the "Wall of Books" scaring away folks. Ok, fair enough. Why not add something to the new OGL (or whatever it's called) that states that the cover of your 3pp has to clearly state that this is not official material? Something that clearly marks it as "Optional" and not part of the core game. That would solve the problem wouldn't it? Those that want the rules, can get them, and those that don't can easily ignore them.
D&D has a couple of accidents of history that prolonged the life of one or two of its editions. The Lorraine Williams takeover of TSR almost certainly delayed the release of 2E, which Gary Gygax was beginning to consider at the time. Meanwhile, the bankruptcy of TSR also delayed work on 3E! (Which likely wouldn't have been like what we got).
D&D has a couple of accidents of history that prolonged the life of one or two of its editions. The Lorraine Williams takeover of TSR almost certainly delayed the release of 2E, which Gary Gygax was beginning to consider at the time. Meanwhile, the bankruptcy of TSR also delayed work on 3E! (Which likely wouldn't have been like what we got).
Cheers!
If Gygax had produced 2e in 1985 instead of being ousted then 1e would have been going for 8 years.
If TSR had produced 3e in 1997 instead of being purchased by WotC then 2e would have been going for 8 years.
So even if the edition life cycle had been extended then they would still have had a good solid shelf life.
But, is it though? Is eight years (or even ten) a good solid shelf life?
I imagine this is a legal issue that's being gone over with a fine tooth comb/tied up in red tape at the corporate level because of the success of Paizo.
Just spitballing, but, what if they did an OGL with a 10 year limit? Say that the license is good until 2026 (if it came out in 2016) with the option of being renewed. Would publishers go for it?
It seems equally possible that the reason the legal issues involved haven't been resolved is that they aren't important enough to be a priority.
I was thinking about it this way:
WOTC continues to focus on its Organised Play stuff - with the two "big tent" releases per year. It then bangs out an OGL for those of us who want extra stuff.
Wouldn't that be the best of both worlds?
Yes.But, is it though? Is eight years (or even ten) a good solid shelf life?
First, so what?If you look at other hobbies, things that are replaced every ten years aren't really considered to have a great shelf life. Boardgames to revamp their rules every ten years, at least, not the popular ones.
Even at ten years, we're still talking about spending about 20% of the lifespan of an edition building the next edition. It generally takes two or three years to produce a new edition. So, we're talking about hundreds of thousands of dollars, if not millions of dollars, being sunk every ten years to come out with the next edition.
Is it worth it? I don't know. I honestly have no idea. But, I'd be a lot more comfortable if we had twenty year gaps between editions. That we could have a stable game for a couple of decades before getting a new one.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.