Personally I feel the reason Metal Gear is doomed without Kojima is that I have zero confidence in Konami as a whole at this point.
I feel the reason why Metal Gear has remained a quality series is because of the pull he had so even with other series being abandoned it completely ruined, he had enough stroke he could continue to do what he did.
This doesn't mean that someone else couldn't have taken the series over, I fully expected Kojima to hand the reigns off eventually when he felt like his staff could manage, but in this scenario I still believed he'd be overseeing development, and more importantly using his influence to protect their work from the incompetent suits who would otherwise destroy it.
I do think that even in this case it would feel a bit different and in general it would be best if the creator of a series got to continue to work on it though.
I hear you, his work definitely feels more like that of an auteur than many game directors, even his peers creating of AAA game franchises. That's why I'm hoping if there is a new MGS game it's part of a new saga that only plays like previous games and carries the spirit of his storytelling. There's not many creative directors and teams out there who can put together games that absolutely no other game developer can come close to duplicating - Hideo Kojima, Fumito Ueda, Suda 51, Tim Schafer, Lorne Lanning and a handful of others on that list.
If it's any consolation, it could be much worse - at least Kojima's MGS saga already has an ending. Everything since MGS4 is pretty much just fleshing out the mythos. Pretty lucky in that regard, since a lot of beloved story-based IPs end on cliffhangers when the auteur moves on to make something else.
Also, keep in mind that Konami is a major business and like most businesses they play the press game. You only know that their PR folks want you to know. And knowing how smart Kojima is, it wouldn't surprise me if he knew which way the winds at konami were blowing in mid or early development of TPP and allowed himself to construct an satisfying conclusion with few if any loose ends.
Many great game developers in podcast interviews have described the game development process as a very fluid, in the moment type way or working where the direction of the project can change at any moment. So, if nothing else, MGS fans might be able to rest easy knowing that Kojima will leave us with a complete version of the experience he envisioned for much of his career.
And now the exciting part: After nearly 30 years of seeing what he can do with one IP, now there's a strong possibility that we'll finally get to see what a fresh AAA original IP from an industry rock star who's spent his career mastering one will look like.