Timeline based on information I know.
2018
- Retro initially intended to remaster/remake the entire Metroid Prime Trilogy.
- But Nintendo hands Metroid Prime 4 to Retro Studios.
- Retro now has less time to work on trilogy, so they focus energy on finishing Prime 1.
2019
- Nintendo begins looking for external studios to provide additional help + assistance to Retro Studios.
- Original plan: Core work (engine, art assets) on Prime 1 could
"potentially" lead into sequels: Prime 2 and 3.
(Don't get your hopes up for this)
- Original plan: Prime Trilogy games would be developed and released sequentially. (Prime 1 would be developed and released first)
2020
- Covid-19 pandemic has a negative impact on the entire game industry.
- Many game developers are now working from home.
- Everything has become more complicated.
2021
- Metroid Prime 1 finally wraps up development.



- Prime 1 remaster is a bit more ambitious than anticipated.

------------------------------------------------------------------------
- It's currently
unknown whether Nintendo
scrapped/cancelled future plans for remasters/remakes of Prime sequels.
- No journalist/insider seems able to get a clear, straight answer on Nintendo's plans for Prime 2 and Prime 3.
- An insider named
Belmont (on Resetera)
seems convinced plans for Prime 2 and 3
were scrapped. (Source)
2022
- It's Metroid Prime's 20th anniversary.

- Switch also turns
five years old.
2023
- Metroid Prime 4 aims for a release this year.