The NBA offseason is heating up, and the Boston Celtics will be faced with a pivotal decision regarding their future as well as the future of one of their main stars.Boston is reportedly exploring ways to acquire Milwaukee Bucks superstar Giannis Antetokounmpo, which could involve moving All-Star forward Jaylen Brown to a third team.According to MassLive’s Brian Robb, Boston’s interest in Antetokounmpo may force it to chase realistic Brown trade…