For sure players are breaking through at an older age nowadays. As you can see girls like Sharapova and such broke Top 100 when they were 16. Nowadays that's almost unheard of, the best girls of the 1992/1993/1994 group (McHale, Babos, Stephens and Robson) all broke Top 100 when they were 18.
Donna Vekic is now 16y2m and ranked around the #120 mark. She's about 120 points away from Top 100 at the moment. Azarenka, Ivanovic and Wozniacki all broke the Top 100 at 16y11m so I wonder if she can beat them. Although of course nowadays breaking through younger is a bigger achievement. 7-8 years ago breaking Top 100 as a 16 year old was not that uncommon but nowadays doing it before 18 is almost unheard of, that's why Donna is such a rare case. It'll be interesting to see if she can do it.