SpaceX has 3 cores that are spoken for and awaiting their official government reuse: B1061-2 (Crew 2), B1062-2 (GPS III), and B1063-2 (NASA science mission). Once those are reused by the government agencies then they should be freed up for other SpaceX launches. I can only see the NASA science booster being held for another NASA launch possibly.
Which leaves the SpaceX workhorses of B1049 (at 9 launches), B1051 (at 9 launches and heading for 10), B1058 (at 6 launches, and B1060 (also at 60.
There are the two Block 5 FH side boosters that were flown twice and are still sitting around almost two years: B1052 and B1053. Maybe SpaceX is holding onto these for a future FH fully expendable launch.
Lastly, SpaceX has an entirely new FH built for an upcoming military launch (USSF-44) this year.
So, yes, SpaceX is very thin on F9 boosters with two of their workhorses reaching their possible refurbishment dates. SpaceX could use about two or three more boosters to keep the rapid launch turnaround times going.