Comment by MertsA

There's a decent chance that they might not. They've been making more and more improvements to Falcon 9 in later blocks. In particular there's been an effort to improve reusability of the later designs. Currently SpaceX is having more and more used Falcon 9s piling up. Who knows for sure, but at the moment they have no shortage of reused rockets and it's preferable to them to start using the later designs.