The prevalence of touchscreens has probably resulted in a decrease in average fingernail length
I feel like I used to see a lot of women with super long nails struggling to use their touchscreen phones. I'm sure at least some of them have chosen slightly shorter nails to make it easier.
Eh technology will change again, before we see any major changes.
I remember reading some fifteen years ago that due to texting on an oldschool mobile phone, our thumbs might evolve in a new way because we all of a sudden used thumbs in a new way. Some scientists predicted we'd started using thumbs for tasks we'd otherwise use our index fingers for.
It could, however, make a social trend for shorter fingernails (primarily on women, I imagine). Just meaning people are more likely to trim their nails shorter.