(I haven't finished reading it yet.)

Yeah, I had forgotten about population aging, though I'm not sure how big an effect it is. I'd guess the median age (in Italy) has increased between 5 and 30 years in the past 45 years.

From the abstract:

the direction of [intracohort] change is most often toward increased tolerance rather than increased conservatism

That's what happens in diachronic linguistics too: when adults change the way they speak, that's usually towards the way younger cohorts speak rather than away from it (just google for Queen vowels). In absence of any population aging, that would only accelerate linguistic changes among the population as a whole.