i do think Graduation or words relating to that wouldnt be used until the 3rd SH film, since Peter would be a senior by then and it would be more appropriate to use it for that.
so the 2nd movie... we know that Peter will be a Junior by then, BUT its gonna be after the events of Avengers Infinity War-- so as much as we think its gonna be titled all highscool-y, will that actually happen? i mean we know Homecoming is related to highscool life as it is a double meaning in RL, but i cant expect the 2nd movie to follow the same logic. the plot of SH2 would at least revolve around 3 main pillars of the Spideyverse-- Peter as a Junior, Peter as an Avenger(ish) and Peter as a survivor of the Infinity War. what on earth are we gonna call a movie like that?