Since summer, NG only used the B763 on the MIA run, obviously to free up the B777 for their Asian-Australian-services.
I don´t see NG (res. OS) serving the VIE-MIA market nonstop soon. With not more than 30-60 pax on board ex VIE bound for MIA via MUC, there aren´t enough passengers to support a nonstop service from VIE.
On the other hand, the MUC-MIA route is a very popular one. Seeing the fact, that this cut (VIE-MUC-MIA) is only a temporary suspension, i´m convinced, that NG will pick up the route again as soon as possible or perhaps OS itself steps in with their own a/c, who knows.
If this suspension turns into a permanent cut, LH would look to fly this route itself for sure. Perhaps we can´t expect a LH service starting the next year, but after one or two years, there should be enough demand for a daily A343 service. Don´t forget, LH didn´t increase capacity between FRA and MIA for quite a long time now. So a second daily MIA service ex Germany might already be on their list.
But i still see the NG 763 as the ideal a/c to operate the MUC-MIA route.
By the way, the DL (JFK suspended, while ATL still served) and AC (YYZ suspended) cuts are only temporary at the moment. Both airlines should be back in MUC for the next summer season. The only routes, which have been discontinued definitly, are the trice weekly Malaysian to KUL and the twice weekly Air Namibia to WDH. It´s disappointing, but the situation is not that worse (only 5 weekly flights lost so far) in my opinion, as LH and the Star Alliance carriers will stick to Munich (latest proof: surprising increase in flights to Asia, PVG and HKG, this winter), there´s no doubt about it.