To gradually increase the number of slots for validators, I propose scheduling the increase over time for 200 slots. The scheduled event mechanism (submitted by external motion to council and then pass to referenda queue for vote) aims to increase the number of validator slots steadily upon certain conditions. In the case of Polkadot:
This mechanism can be canceled or completed after 100 eras, and at that moment the community will be able review network metrics. The proposal aims to avoid an abrupt increase in the number of validators on the network and follows the recommendation of the parachains team as noted here.