If the unit is a 406v2 (the one with integrated station ports) and the sticker on the bottom or back has a PCS of 8 or above then yes it can go to 4.0+.
If it is a 406v2 with a PCS of 7 or below Avaya has issued a PCN for the replacement of these units at no cost.
Kyle Holladay
Certified: ACACN, ACSCI, ACSCM, TIA-CTP
ACE Implement: IP Office
"If it worked the way it should you wouldn't need me