In the Post-Mission Press Briefing [1] Elon Musk said SpaceX will gift the stage to "the cape" (so either NASA Kennedy Space Center or the CCAFS) because it's historic. Also, they don't need to keep the Block 3 cores, they want to transition to Block 5 as soon as they can to get the 7 flights of a frozen configuration of Block 5 to get certified for flying people.

1 - https://www.youtube.com/watch?v=jC3LQFpuzqs