As long as all three division winners and us make it into the top 4 we'd have homecourt advantage in the first round, I think
The way I understood the new rules it works like this.
The Grizzlies only need to be one of the top 4 records in the conference to have home court advantage in the first round. However seeds are determined by the division winners and the next best record in the conference.
As an example, if San Antonio wins the Southwest division but finished with the 5th best record in the conference the Spurs would be the 4th seed but the 5th seed (the team with the better record) would have home court advantage in the 1st round.