Even if the autopilot disconnects due to one or other reason during the rapid depressurization, the aircraft should be trimmed, so no significant deviation from flight path would occur. It doesn't take even 10 seconds to take the mask on (without the headset) and even if aircraft goes into 3000ft/min climb/descent for some reason, you will still be (in worst case scenario) 500ft from your originial altitude, so still 500ft separation if traffic is immediately below/above you.
In my opinion, during the rapid depressurization there are only three steps that have to be done ASAP: mask on, check oxy regulator is at 100% and establish communication. Then you have time to do couple of deep breaths and proceed with the required actions.