We have SD DirecTV at the house which we use in the RV when travelling.
The RV has a KVH  TracVision L3/S3 antenna.

We are planning on upgrading to DirecTV HD Genie which includes installing new HD antenna at home.
I asked AT&T/DirecTV if the HD Genie would work with the SD TracVision antenna (I don't expect HD quality TV).
After a week checking with their Tec Support they still don't have an answer.

Is anyone using HD Genie in their RV with SD antenna?

If you don't get an answer here try tv4rv.com, he would know.

The very simple answer is that the Genie is a "SWM-only" receiver and the TracVision is not a SWM dish.  However, many non-SWM dishes can be used with SWM receivers if they are properly modified.  If the TracVision has two coax outputs, it is highly likely that it can be used with a Genie by following the instructions in this document.    Although the document addresses Winegard systems it can be used as an outline for how to use MANY non-SWM dishes with SWM receivers.  Basically, all you need to do is connect the two coax outputs to a SWM8 switch (which can be mounted on the roof of the RV).  Then take a single coax from the SWM8 inside the RV and add a PI29 power inserter in line with the coax going to the receiver.  Guide for using non-SWM dishes with DirecTV SWM receivers