If they can squeeze it into a watch... possibly. I don't know.
It does seem to be a bit bigger jump than normal for an S cycle. Correct, they haven't changed screens mid cycle either.
We may get a hint at WWDC.
3GS- Speed
4S- Siri
5S- Security
6S- Sensation? Sensitivity? Sense? Screen?
Aside from the 3GS I can't say I recall Apple making references as to what the S stands for, aside from perhaps people finding their own definitions.