As for the Celtics, they are going to make Irving a maximum offer, and perhaps their case gets stronger with Irving knowing that Durant is either 1. not going to be healthy for at least a year and 2. perhaps considering returning to Golden State.
One of the teams that are in the running for Irving is the Brooklyn Nets and now, sports retailers are preparing for Irving's departure from Boston. Irving could land a 30% max deal for five years with 8% raises in between.
Irving could also maintain future flexibility by signing a 1-plus-1 with the Celtics (or any other team), although that would open him up to more questions about his future, which irked him all year in Boston. If Irving looks elsewhere he'd be limited to four years and 5% raises, or just over $140 million all-in. And Kyrie Irving certainly has a significant interest in being back in NY.
National Basketball Association rules state that teams may not acquire more than one player signed to such a deal at one time. Irving's Rose Rule, signed with the Cavs back in 2014, officially began in 2015. In the backend of his career at 31-years-old, he's one of the best players in the league and one of the most consistent ones as well.