Originally posted by lol101 Let's see, starting from the K-mount debut in the mid-70s:
K series, M series, A series, P series, SF series, Z series, MZ series, *ist series, *istD series, KD series.
To be fair, the *ist series was a "series" of 1, but indeed a new concept (like the LX).
On the other hand, the move from *istD to KD was hardly a new concept, but more like a change in the naming system.
Pentax dslrs so far, from *istD to K-m, are pretty close in "concept". So maybe it's indeed time for a bit of a shake-up!