If it had been anybody but Hermione asking him that, Severus would have had a biting, sarcastic reply at the ready -- something along the lines of were the lack of white hair and wrinkles her first clue. As it was Hermione asking him that, however, he simply sighed again and nodded.
"I do realize that, yes," he finally answered, still frowning. "But he might not even want to know what the future holds for him, and if he doesn't, I don't think it's my place to tell him. I mean, I specifically asked you for information about what happened because the outcome of the war was very important to me. But this is all ... eighty years in the future for him. It can't be more than an abstraction for him." Which, now he thought about it, could be seen a point in favor of telling Dumbledore, rather than not telling him. He reached up to rub his eyes then, with yet another sigh, because he seemed to be going out of his way to spare Dumbledore's feelings -- more so than was strictly warranted for someone he didn't like, that was. So Hermione would probably see right through him before too long at all.
It wasn't that he didn't like Dumbledore. He'd actually started to care about the old bastard, in spite of the slights of the past, and he'd thought they'd established a working relationship at least based on mutual respect. Until he'd found out that Dumbledore had been lying to him and using him all along, that was. And that revelation had hurt, more than he cared to admit, even now. He just didn't want to open himself up to being hurt like that again. Because in spite of his age, Dumbledore was still capable of doing something like that to him. Therefore Severus had been particularly nasty to discourage any sort of friendship, in order to protect himself. Hurt them before they could hurt him. That had been his modus operandi since he'd been all of sixteen, and he saw no need to alter that pattern now.