If the NBA expands to Seattle and Vegas, the alignment changes I see happening are Vegas replacing Phoenix in the Pacific, the remaining MT/PT teams forming the Mountain, Oklahoma City to the Southwest, and Minnesota to the Central.
Then the NBA can adopt a new regular season schedule format heavy on division games in an effort to make divisions manner in one sense again. Teams in the 5-team divisions would play 7 games against each division opponent, for 28 division games, and teams in the 6-team divisions would play 6 games against each division opponent, for 30 division games. Every non-division match-up, even those between teams in the same conference, would be played twice (home and road).
For Minnesota, going from playing 10 games against the Central Division to 30 would allow the Timberwolves to develop significant regional rivalries, which they have not yet been able to do due to being in the Western Conference their entire existence. The rivalries of the expanded Central Division could become so intense that the Central is given the nickname of "Black and Blue Division" like the NFC North, which effectively has teams in four of the same Midwestern markets that the NBA currently has teams in.