For their last few games, Bethesda have preferred to keep details about their current in-progress game to an absolute minimum and then release a trailer and confirm the release date just a few months out from release; they announced Fallout 4 on 14 June 2015 and released the game on 10 November the same year. They then announced multiplayer spin-off Fallout 76 on 30 May 2018 and released the game on 14 November the same year. So it's entirely likely that they will repeat the same format when it's time to fully unveil Starfield to the public.
Bethesda issued a new copyright claim for Starfield with a date of 2021 just a few weeks ago. Games companies usually only issue copyright claims for the year of release, indicating that Bethesda are indeed planning to release the game before the end of 2021. Note that this is not set in stone: if the game was delayed to 2022, they could amend the copyright claim to that year instead. So this is not cast-iron 100% proof that the game will come out this year, but indicates strongly that this is their current plan. Certainly last year, Bethesda claimed that this year would be the earliest fans could expect to hear more news about the game.
Microsoft, who completed their purchase of Bethesda a few weeks ago, will no doubt be keen for the game to come out this year to strengthen their portfolio of games launching this winter. That includes Halo: Infinite, the first Halo title in six years, and reportedly a new Forza racing game. Unconfirmed reports also suggest that Starfield will be exclusive to the Xbox platform on console, although it will get a PC release as well. PlayStation owners will be left out in the cold, as many feared would be the case when Microsoft acquired Bethesda.
If this news is accurate, it could be confirmed as soon as E3 2021, which runs from 12-15 June; Bethesda confirmed their last two release dates at E3 events in 2015 and 2018.
Although it appears likely that Bethesda are targeting a 2021 release date, there is one fly in the ointment, namely the ongoing COVID19 pandemic. Like most developers, Bethesda have mostly been working from home which has slowed game development and quality assurance down. If there are major bugs or problems found in this process, the game could be delayed into 2022 fairly easily.
Bethesda are also working on a new Elder Scrolls game, the follow-up to the massive-selling Elder Scrolls V: Skyrim, which celebrates its ten-year anniversary this year. That game is not expected to be released until 2024 at the earliest, and potentially a lot later than that. A new Fallout game is even further off at this point, unless Bethesda collaborates with another studio to help them get their games out faster.