Hard to say. I love basketball. It's my favorite sport to play and favorite to watch, but I'm a huge Blazers fan. If they left, I may try to find another team to follow. I grew up a Bulls fan, but that was back in the 1970s. I don't really feel a connection to that franchise anymore.
I also grew up a Cubs fan and a Bears fan. Even though the Cubs are having a magical season, I haven't watched a single Cubs game in the last 25 years. I was still a Bears fan when they won the Superbowl back in 1986, but haven't really followed them since Walter Payton retired.
I briefly adopted the Seahawks and Mariners when we lived in Seattle, but haven't followed either team for years - other than watching the Seahawks in the Superbowl the last two years.
So, not sure if I'd give up basketball all together, but I would definitely watch a lot less with no local team to connect with. When we first moved to Oregon, we went to a LOT of Blazers games at the old Memorial Coliseum. Attending so many games in person made it really easy to feel connected to the team. So, even if I adopted another NBA team, I don't think I could ever be as fanatical about another team as I am about my Blazers.
BNM