Yeah, I beat KH3DS, and they should have been hinting at a KH3. Assholes.
Remember the "random" letters that appeared during the credits? They spell out something like "Next is Kingdom Hearts..." then you get Riku and Sora heading into light, their silhouettes curiously making what looks like a Roman numeral "III"
And unlikely we'd see an HD "collection" without the other three games. I'm guessing BBS, KHII, and whatever the other one is in a different HD bundle... possibly a year later... meaning 2 years before KHIII, I'm guessing. :P
You're not SERIOUSLY overthinking this, are you? Your assumption makes no sense. So if I were to put Mickey in between the two of them, it'd be a secret hint in Egyptian or something?
Also, the secret message isn't really hinting at this. I'm pretty sure that making a collection like this takes FAR less time than doing a new entry altogether.