If I queue with my friends who were in the same rank as me last season and play all my placements, will we be placed in the same rank?
Not necessarily. Placement ranks at the end of the 10 calibration matches are based on (from experience) final SR from the previous season, individual performance during the calibration matches, difference in the party's SR, and possibly more factors that Blizzard hasn't disclosed.
For season 6, it was possible for a party of players in the same rank to play all 10 calibration matches together and end up in different ranks. Note that this is also possible during normal matches: SR change after each match won't necessarily be the same for players in the same party.