None.
I have bought and am trying to learn to use DeLorme Street Atlas. It is really focused at setting up routes for trucking companies - and much better at setting up smaller repetitive routes.
Unfortunately in my opinion - the future is on-line with an account with Google Maps or something similar.
I seriously doubt there will ever be anything as flexible, as customizable, as useful as S&T - even with it's few quirks.
The RV market is simply too small to justify the expense of developing a standalone program like S&T and buying all the base data necessary to make it useful.
The 'good news' is that S&T 2013 will be useful as long as you own your current computer, and likely the next one.
We will have to do some more research for new highways, updated interchanges in major cities. I do use DeLorme for that.
We will soon have to start verifying the campgrounds are still open, etc.
But the basics of the highway network are not going to change for decades - so S&T will still be the best tool to sit down on a winter evening and plan/dream about trips for next summer, especially if you are at a campground without an internet connection.