The new srilankan players were given a chance and they really performed well. It does not matter much how many of them will play in the next Srilanka ODI / T20 as the experienced players are still experienced but we can see the future of srilankan cricket team is bright as they have new emerging players and they have many more years to play.
The "experienced players" were given lot of chances. And what did they achieved recently? According to the ICC rankings, Sri Lanka is ranked 6th in tests, 8th in ODIs and 7th in T20Is (they were ranked 9th, but after the series win against Pakistan they gained two ranks). And their ODI ranking would have been much worse, if Lasith Malinga was not playing in the series against New Zealand.
This is what the experienced guys achieved all these years:
1. They failed to advance to the semi finals during the 2019 Cricket World Cup. Finished with just 3 wins from 9 matches.
2. Failed to qualify directly to the 2020 T20 world cup, as they failed to secure a slot among the top-8 ranked teams.
3. Suffered an innings defeat to NZ at home this year.
I believe that it is time to say goodbye to most of these "experienced players".