Carlos Alcaraz has been the youngest top-100 player for a while but as time passes it was a given that somebody would replaced him and it happened.
Thanks to his triumph at the Sanremo Luca Van Assche entered the top 100 for the first time in his career and he replaced Alcaraz as the youngest player in the top 100. The French player was born in 2004 and will turn 19 on May 11. Alcaraz obviously is already a 19-year-old and will actually turn 20 six days before the French player turns 19.
Seeing Alcaraz emerge in the way he did inspires many young tennis players who are making the push to become main tour regulars. Van Assche is only one of many young players emerging right now and it's a trend that will keep going. After all, players like Dominic Thiem who were once considered the Next Gen when compared to the big three are starting to turn 30.
Medvedev is closer to 30 than 20 so a shift on the Tour is clearly happening.