Sig has already called for a “voluntary upgrade”. You can go to their website to get all the needed info for returning your gun for the fix.
Just registered both of my P320. So, somewhere in next few weeks, they get shipped in and take 4-6 week turnaround time. Sig is paying all costs--shipping costs they mention--and presumably any FFL transfer fees since, unless I am mistaken, I cannot send/receive the gun directly because of federal laws.
I like my Sigs and luckily have alternatives while these are being fixed.