Spendor is building a few 2 1/2 way speakers right now. You can read a few reviews on their line to get more information.
An undriven passive radiator is not considered as part of the equation when considering the divisions of a speaker. Technically, a passive radiator is merely another form of ported speaker with the additional, non driven speaker providing controlled resistance and frequency extension that can't be achieved in a typical vented design. So a three way speaker is a three way speaker whether it has a passive radiator or not.
A "X and 1/2 way" design refers to two (or more) drivers covering the same region with each driver having a different cutoff frequency. This is most often done in the lower frequencies. If the cabinet contains two 8" low frequency drivers both will operate from the low frequency limit and upward. One of the two 8" drivers will roll off at 250Hz or so, therefore it is supplementing only the lowest few octaves. Both drivers handle the same extreme low frequencies but both do not handle all the same upper frequencies. Between 250Hz and 800Hz only one of the 8' drivers is doing the work. (In this example the stated frequencies are for explanation only, in any design the rolloff of a driver will take one octave to be down at least 6 dB in level.)
How this division works out can change according to the design. But when two (usually) similar drivers carry some but not all the same frequencies, the design is considered a "X and 1/2 way" system.