In my mind, this is the most tactful way to continue the series. I don't think Kojima would ever be directly involved in a hypothetical sequel, although I also get the feeling that Platinum senior management would want to get Kojima's approval to take the project on themselves.
I think it's perhaps still unlikely, and maybe they'll just do some kind of MGS6 without Kojima and all the other staff that left, or maybe remakes, but I wouldn't rule it out.
It is a shame, too, since Platinum did an incredible job of this game, given it was a salvage job in the first place. I can only imagine how good they could make a sequel when built from the ground up to be an MGR game. Especially if they were able to implement the cut features like increased mobility options like wall-running and such.
Still the best Metal Gear imo.
Maybe the right way to do it would be to get everyone hyped up to play another game as the complete badass Raiden, but then to subvert your expectations less than an hour into the game, you end up having to play as Solid Snake.
Edit: footage of the wall running mechanic from before release, which sadly had to be cut
