Are you sure they reintroduced a proper firewire controller?
It was discussed here, and in other places.
https://forums.macrumors.com/threads/523579/
I don't have that model, but I read that the Penryn MBPs reintroduced the TI controllers, instead of the Agere ones that caused problems with many FW audio interfaces.
Hopefully they will stick good ones in the update; they had so many complaints before it is hard to believe they would not.