How can I 'update' from sanctuary to temple? Should I just generate another masternode key and use a new alias?
Yeah, you can, but be aware there is a pitfall that affects all masternodes when rebroadcasting same public IP with new VIN.
I recommend spending the old vin first in coin control. Enable coin control, from settings, go to send money, and spend the 500k.
Then, create your new vin except the only change being with 15MM BBP instead. Also, make a new masternode privkey. Restart the Temple.
Restart the controller. Reactivate the temple (by sending the start command from the controller). Then look at the logs in the temple and see if the new VIN was accepted.
So far, I just brought one temple online. We have 4 people on 1049 and 2 on 1048. Meaning that the supermajority has upgraded.
Now we have to see if these nodes vote that the temple is paid, so far I have not received a payment, but its only been an hour.