If I'm Kawhi Leonard, I'd have serious doubts about re-signing long term with the Spurs.
It's been a great ride there for him but he's 23, coming into his prime, and:
1. Duncan, Ginobli and Parker are two steps from retirment
2. Who knows how much longer Pop will be there as well
3. So unless they can go sign something like Love and Gasol or Aldridge and Gasol, etc.,
What, really, is the attraction for him to stay there? A sign and trade to a young contender makes the most sense to me.
Otherwiase he could very likely end up wasting the next 3-5 years playing on a so-so team (at best) in San Antonio.