Chuck,
There were rumours of a replacement for the 3.6 when I worked there, back in 1998, so don't wait. (Of course now that I say that, they'll probably release its replacement tomorrow)LOL!
The probem we (it was we back then) had, was that the damn thing just kept selling, or as Kathy Gornik, President of THIEL said, "They still have legs."
I personally never liked them because they had way too much of their own personality for ME. As someone said 'Vive la difference'.(I did not study French, as you can see.
Plus the sub woofer, in walls, and the final embracing of the Home Theater market, 10 years too late, came along for THIEL.
The other issue, is how to make a product which will 'fit' into the mix, not outperform others in your line, and cost less, killing some of your other products--the worst possible outcome.