trust me the DLC is not coming.
Fixed.
Think about it.
Continuing FO3 was simple... the original end was "Look! Clean water!" Ok, that's simple to build on.
FO:NV? Just the main endings (ignoring all the minor faction changes) would all bring massive change to the Mojave. Each one separate. You'd need an entire DLC (if not a full expansion) just to have the changes for one of the major endings.
And even if you were crazy enough to do that (four or five DLCs, each one representing one of the major factions winning), they'd sell terribly, because each person would only want the one for their end. The others would be useless to them.
So, no. There won't be a continuation.