It's difficult but not impossible to picture Sir Roger returning once again in 1987.
For me, it is impossible, and I say that as Roger's number 1 fan.
Personally, I think "License To Kill" was conceived and produced specifically with Dalton in mind, and engineered to play to his strengths, just as "The Spy Who Loved Me" was the first Moore film that felt like it was written especially for Roger.
I think with TLD we saw Dalton's Bond "under construction," with a "kitchen sink" approach that gave us the expected one-liners, upper-crust sophistication (the opera and symphony scenes) and gadgets, but also dipped a toe into more rough-and-tumble stunts and the hard-edged scenes like Bond as the anti-sniper sniper. (And we now know that other changes, like trimmed dialog and the excising of the flying carpet scene, were also part of the "figuring it out" process). Then I think when the dust settled, the producers looked at the whole thing and said, "What worked here and what didn't?" And at the end of the day, Dalton was competent at the comedy but not as comfy with it as Roger, and while he had nice clothes he didn't wear them with the panache of his predecessors (or successors). But what he DID do remarkably well was the "hard-edged" stuff...the "You should've brought lilies" scene with Pushkin, the "strawberry jam" line in Bratislava, the "If he fires me, I thank him for it" line, the unusually abrasive exchange with M over Pushkin's "kill" order (by this point, we'd forgotten that Bond and M used to have friction).
And then, there's that scene where Saunders is killed, and the balloon rolls up to Bond, and he reads it and pops it with a look of flat-out rage. And if you saw it with a cinema audience, you know this is when it all clicked into place. THIS is the moment when I think it sinks in that the old order hath changed, and there's a new sheriff in town. When was the last time we saw Bond as a truly bad-ass, threatening figure, someone it would be scary to be on the bad side of? I really think someone in the front office looked at that scene and said, "There! THAT'S what our guy gives us that we haven't had. Go out and write me a script with more of that!"
And so they found a way for Dalton to hit that note again early in LTK and keep a mad on for the entire rest of the film (until the end, when he gets all happy and swims around in his tux with a winking fish). Personally, I think that was a mistake, as I find the film very one-note and unrelentingly grim, when Dalton was capable of much greater range than the "one-track vengeful killing machine" we usually associate with inferior actors like Steven Seagal, but different strokes for different folks, I guess.
Anyway, I don't think Roger would've been playing Bond at age 62 regardless, but if by some wild stretch he HAD, we would not have gotten the same film, as this one was written for what the powers-that-were thought were Dalton's strengths.