How many cherub books will there be?

There is no such thing as "Cherub books". You may be thinking of the "Cherub" series by Robert Muchamore, which is a series of spy novels for young adults.

There are currently 13 books in the Cherub series:

1. The Recruit

2. The Fall

3. Maximum Security

4. The Killing

5. Divine Madness

6. The Sleepwalker

7. The Shadow

8. The Recruit's Guide to Deadly Skills

9. The Judas Strain

10. The Nowhere Man

11. The Reapers

12. The Ghosts of Manila

13. The Chain

There is also a standalone novel called "The Spy Who Came in From the Cold".

Therefore, it's impossible to say how many "Cherub books" there will be in the future, as the author may continue writing the series.