The 777 and 747 will not be updated, they will be replaced by completely rebuilt versions which are (AFAIK) currently under development.
They're too old, the work required to update them to be up to the current standard PSS wants from their products would be too much.
Existing customers will get a discount on purchasing the new version.
The Airbusses will most likely be updated. PSS hasn't officially announced it, but that's my expectation.
Soundfiles should be no problem. MSFS for a long time now has used standard Winows WAV files which have built-in support in DirectX. I don't see Microsoft changing to a 3rd party format when their own works perfectly well and has tight and good working API support in their own APIs