Shulchan Aruch emphasizes the importance of davening the Amidah with the rest of the tzibbur.
If one is in shul and there are 8 or 9 people, should everyone wait before starting Amidah to see if others may soon come in to form a minyan? How long are they required to wait? Do they need to wait at all, assuming that they will not pass a z'man like last time for Mincha.