SpaceX is trying to launch Starlink satellites every week. They launched 240 satellites in March. They should have 3-4 launches in April. If they get 25 more launches in 2021 they will complete the first and second 1440 satellite orbital shells.
An average of one per week launch and reaching 38 total successful launches will let them complete the first three satellite orbital shells and have about 3600 satellites in orbit. Nine more launches completes all five orbital shells for the 4408 Starlink satellites in phase 1.
In April 2020 SpaceX modified the architecture of the Starlink network. SpaceX submitted an application to the Federal Communications Commission (FCC) proposing to operate more satellites in lower orbits in the first phase than the FCC previously authorized. The first phase will still include 1,440 satellites in the first shell orbiting at 550 km (340 mi) in planes inclined 53.0°, with no change to the first shell of the constellation launched largely in 2020.
First shell: 1,440 in a 550 km (340 mi) altitude shell at 53.0º inclination.
Second shell: 1,440 in a 540 km (340 mi) shell at 53.2º inclination.
Third shell: 720 in a 570 km (350 mi) shell at 70º inclination.
Fourth shell: 336 in a 560 km (350 mi) shell at 97.6º.
Fifth shell: 172 satellites in a 560 km (350 mi) shell at 97.6º.
There would then be 7500-8000 satellites in a phase 2 and then 30,000 satellites for phase 3.
A 300 Starlink per month deployment rate in 2022 and 2023 would let them complete phase 2 by the end of 2023.
Increasing to 600 Starlinks per month would take until 2027 for the 30,000 satellite phase 3. SpaceX would also need to replace the first wave of satellites starting around 2024.