Hi mh,
There was no functions for sanitary sewers specificially in LDT. C3D currently has no calculation capabilties for sanitary sewer or pipes at all. Just recently, Autodesk purchased Intellisolve which is a hydrology and hydraulics program that you could probably use for your sanitary calcs. It's available for download for subscription customers. This is an add on program and doesn't work within C3D. You can import and export the pipe data via LandXML but that's the limit of the conectivity with C3D.
As far as what is coming, Autodesk won't release that information. They are a publicly traded company and if they say they are going to release something and they don't release it that quarter, they get fined by the SEC (Securities and Exchange Commission). There's a saying in these discussion groups that pretty much sums this up, "Those that know, won't say. Those that say, don't know."
Brian