There are basically three or four choices on the table. The "deadline" would be June 29.

KD can opt in for the second year of his one and one, and get $31 million for next season. He probably sits out the season, possibly comes back at the end of the regular season, right before the play-offs (the Warriors certainly won't rush him). He can then become a free agent at the end of the next season.

KD can ask Lacob for a max extension right now. The Warriors will always have the ability to pay him the most for the most amount of years. He can sign with the Warriors for more than $210 million for five years. The Warriors would essentially be paying him $210 million for four years. If KD asks for this, I don't see a scenario where Lacob turns him down.

KD can opt out on June 29, and become and unrestricted free agent. He could still resign with the Warriors for the max, or sign somewhere else for 4 years, ~$160 million. If he decided he wanted to play elsewhere, it would take a lot of the teams of the table. Clippers, Nets, Boston, and Lakers are all in "win now" mode. The most realistic destination not named the Warriors would be the Knicks.

Or, KD could work out some other new deal with the Warriors, like another 1 and 1 that would begin after next season.