Allo - my $0.02
"Does this thing really decode QS by the book?"
Yes, only it's the entire book, that wasn't able to be practically applied back then due to the limitations of technology.
Plus we've written a few extra chapters in that book. Don't worry, it still has a happy ending.
"Part 2 of question (which is actually more important to me): Will the model based on SQ be able to decode SQ by the book? And I mean with Tate like performance or better. Also, will this model be able to still decode QS with accuracy?"
In short, yes. The SQ part will be SQ by the book, and that model will not have the TSS mode, it will simply replace the TSS mode. So it will be our QS based decode, and the SQ decode.
As I think Charlie said, that comes next year, however we will be able to do conversion on the TSS units, for only the cost of shipping.