Non-shorting Rotary Switch "dead" Time
On the rotary switches that I've used, the dead time between positions depends entirely on the speed with which the operator turns the switch.  It may be possible for a careful operator to "park" the switch between positions, so neither contact is made, and the dead time becomes infinite.

(added from a comment)

Propogation time for most logic gates is measured in nanoseconds. I'd expect the open circuit time for a manually-operated switch to be at least several milliseconds, (although I've never measured it), so the switch "dead time" will be much, much longer than any likely propogation delay. If you are really concerned, you will have to measure it yourself, as it is not something that the switch manufacturer can measure in any meaningful way