I talked to support yesterday, and they said FortiOS 5.4.2 was (17 Oct - 1 Nov), so any day now ?? ;)
FortiOS 5.6.0 will however be next year, beta has not begun yet.
FortiGate 200A/B, 224B, 110C, 100A/D, 80C/CM/Voice, 60B/C/CX/D, 50B, 40C, 30B
FortiAnalyzer 100B, 100C
FortiAP 220B/221B, 11C