There is a new disclaimer at http://www.navisworks.com/support/formats that is not unexpected after Autodesk acquired NavisWorks.
"PLEASE NOTE THAT SOME THIRD PARTY VENDORS MAY ELECT TO NOT PROVIDE FILE FORMAT SUPPORT FOR NAVISWORKS PRODUCTS AS OUTLINED BELOW FOLLOWING THE SALE OF NAVISWORKS TO AUTODESK." ...
What is quite reasonable to expect is that Autodesk will have more of their products supported with their native formats. Revit really need native support for example.
Via BIM Manager.