Have a number of Cisco ASA 5506-X with FirePower
ASA version is 9.9.2 (56)
What is the ASA upgrade path here (9.10, 9.12, 9.13 ?)
There appear to be some memory limitations
We don't really use the FirePower services if that makes any difference
You can upgrade direct from ASA 9.9 to 9.10, 9.12 or 9.13 without an interim upgrade. Reference here, checkout the section ASA Upgrade Path. Table 1 in the same guide confirms that 9.13(1) is supported on the ASA 5506X
9.13 has only recently been released, I wouldn't necessarily upgrade to that version unless you need a new feature or resolution to a bug fix.
According to :
"No support in 9.10(1) and later for the ASA FirePOWER module on the ASA 5506-X series and the ASA 5512-X—The ASA 5506-X series and 5512-X no longer support the ASA FirePOWER module in 9.10(1) and later due to memory constraints"
So to confirm, the second I update the ASA to 9.10 or later , all firepower services are no longer active
Yes, if you upgrade to 9.10 the firepower module will not be supported. You should remain on 9.9 for the 5506 so that you have the option of enabling the firepower module when needed.
Just to add, FTD software for 5506 is now EOL so if you need Firepower it might be time to start thinking of moving to FPR1010