[Rules] Is passing mandatory the last action of a turn ?

[cjsiam]

Player A can pass on his turn of activation,
the opponent Player B takes his activation,
and then it is Players A's activation again to either activate, or pass again.

The only thing that changes this is if the opponent, Player B, ALSO passes in his immediately following activation---in that
case the turn ends...

Passing does NOT end your turn, just you pass on that particular activation
...like you said, waiting for the opponent to move something into range for example...