Raw files from the new Nikon D810 will not open with either Photoshop CS5.1 or Lightroom 4.  When will a real Adobe solution be available to work with Raw (NEF) files in their native format, using CS5.1 and LR4?

Clarification: this is a user forum; you are not addressing Adobe here.

The answer to your question as phrased is: never.

CS5 is history and it is not longer supported.  There will not be any updates or bug fixes for CS5.

You need to convert the raw NEF files from your D810 to raw DNGs using the free, standalone Adobe DNG Converter 8.6 RC (beta), the first version ever to support that camera..