While I agree he has a good chance of it, Game, I don't think it is a stupid question considering his age and the fact that is an increasingly crowded group among tier 2 players vying for spots in the #5-15 range.
Of course just playing all four Slams should help a lot--and playing more tournaments. He played 7 last year compared to his usual 17--only 28 matches. Let's say he plays 14-15 tournaments at a level slightly below 2014-15, and he's back in the top 8.
The other thing to consider, shivashish, is that some of those players are on a downward turn: Berdych and Tsonga, and of course Rafa who you didn't mention for some reason. But I'm guessing Berdych, Tsonga, and Monfils are all likely to fall out of the top 8 next year, joining Ferrer and Gasquet on the slippery slope of declining 30s. I also wouldn't be surprised to see Stan stumble at some point soon.
I'd group 2017 WTF candidates as follows:
Definitely: Andy, Novak
Probably: Kei, Milos, Cilic, Stan
Maybe: Rafa, Roger, Thiem
Outside chance: Berdych, Tsonga, Monfils, Kyrgios, Goffin, Bautista Agut, Zverev, Pouille, Dimitrov, Edmund
I consider that last "outside chance" group to be alternates for Roger and Rafa, depending upon their health. Some of those guys (e.g. Edmund, Dimitrov) have almost no chance, but I wanted to include all players who have a vague chance.