Not on the 40C. From the firmware images found on the support site, I can only find images going up to 5.2.15. If you need a physical fgt device, I suggest getting a D or E model with at least 1 GB memory. Keep in mind that 6.4 Firmware was newly released and it looks like the 60E is the lowest end model fgt supported on that branch.
Is there a way to install newer firmware, say 5.6 or even 6.0, for the same purposes, without bricking it?
NSE4/FMG-VM64/FortiAnalyzer-VM/6.0 (FWF30E/FW92D/FGT200D/FGT101E/FGT81E)/ FAP220B/221C