There's actually a growing belief that George could decide to stay in OKC (either with a 1+1 kind of contract, or a 4-5 year max). I still think he goes to the Lakers, but ultimately Leonard is the wild card.
But if PG13 does elect to stay, then I think Lebron stays put in CLE and maybe forces the Cavaliers to make a trade (like Sexton + something for Kemba, or something similar).
A possibility is, Lebron opts-in and plays another year at Cleveland, and the Spurs hold on to Kawhi or he gets traded to somewhere not named the Lakers, and then in summer of 2019, Leonard and Lebron both team up in LAL (Deng's contract comes off the books I believe). Or if they work a S&T of sorts for 1 of the stars, maybe Klay Thompson follows in FA as well? (I doubt it, but it's a possibility)
I think LAL would actually like that better than likely having to surrender Kuzma, Ingram AND another future asset to get Kawhi now.