Interesting... Unless its really tuning as stated above, they would have to make changes to the engine or transmission to accomplish better acceleration. I don't see them making many changes to the hardware, as they are using it in almost every new Volvo coming to the USA.
I can see some changes to the sensus just being simple software updates. Those would likely trickle to current model years as service is completed.
I just ordered the 2018. They changed what you get as standard as well as changing the content of the packages compared to 2017 and 2016. in 2018 they give you as standard such things as BLIS, Adaptive Cruise Control, Volvo On Call with engine remote start with a complimentary 4 year subscription (it was a six mo. complimentary for 2016 and 2017 models), and takes away some other things as standard, namely the Nappa Leather on the Inscription (it's still perforated leather though).