That's precisely what I worry about with Zeppelin. OK, they split for non-musical reasons, but they already felt like they were winding down - longer gaps between albums etc. I think the split happened at the right time to leave a "complete" musical legacy (although TBH even In Through The Out Door lacked a certain something).
Indeed -- and Sabbath were in this state, too, with the late-period Ozzy albums getting pretty iffy. The Heaven & Hell album might as well have been a different band. OK, not one that lasted long ;) but it was a shot in the arm for the music while it lasted (before getting iffy again ;)). Likewise, just before Dickinson left, Maiden were getting a bit dodgy; even though they carried on with Blaze, I think what they did after Bruce came back showed improvement. Things were better for Bruce -- and Adrian Smith -- going off and doing something else for a while.
Of course, "Free as a Bird" and "Real Love" aren't shining stars in the Beatles catalogue, though we could try making the excuse that the remaining Beatles were limited to working with leftover scr@ps that were perhaps
not the greatest moments in John Lennon's song-writing career .....
But maybe the new H&H album will be cool, and I suspect that the surviving LZ members would produce more interesting material together than apart (which doesn't mean it would
definitely work ;) just that they'd maybe have a better
chance of doing something cool that way.) Otherwise ... well, I guess whatever riffs Page claims to have been storing up will remain in the closet!
Maybe Led Zeppelin would come up with something fantastic, but if they didn't it would tarnish what went before.
A different name for a slightly different project, perhaps, blending more recent influences from the various separate projects they've worked on (not that Page has done much on his own).
At least they'd never go down the road of bringing in external songwriters or flavour-of-the-month producers.
Or the Santana thing of hauling in loads of younger guests! That woulda been OK if it had just been
Supernatural, I suppose, but then he kept doing it! :P Iommi did the same on his 2000 solo album, with mixed results, I think, but then got back to business on his
Fused album and then with H&H.
Hmmm. Page, Santana, Iommi .... all great guitarists in search of a band! ;)