According to wikipedia, these are the people who might still enter the race.

They have all recently expressed interest in running for president in 2020. This list does not include the 12 candidates who have already announced that they are running and Jay Inslee who will be announcing tomorrow.

https://en.wikipedia.org/wiki/2020_Democratic_Party_presidential_primaries

Stacey Abrams, Minority Leader of the Georgia House of Representatives 2011–2017; Democratic nominee for Governor of Georgia in 2018

Michael Bennet, U.S. Senator from Colorado since 2009

Joe Biden, Vice President of the United States 2009–2017; U.S. Senator from Delaware 1973–2009; candidate for President in 1988 and in 2008

Michael Bloomberg, Mayor of New York City 2002–2013

Sherrod Brown, U.S. Senator from Ohio since 2007; U.S. Representative 1993–2007

Steve Bullock, Governor of Montana since 2013

Bill de Blasio, Mayor of New York City since 2014

John Hickenlooper, Governor of Colorado 2011–2019; Mayor of Denver 2003–2011

Eric Holder, U.S. Attorney General 2009–2015; Acting U.S. Attorney General in 2001 from Washington, D.C.

Terry McAuliffe, Governor of Virginia 2014–2018

Jeff Merkley, U.S. Senator from Oregon since 2009

Wayne Messam, Mayor of Miramar, Florida since 2015

Seth Moulton, U.S. Representative from Massachusetts since 2015

Beto O'Rourke, U.S. Representative from Texas 2013–2019; Democratic nominee for United States Senate election in Texas in 2018

Tim Ryan, U.S. Representative from Ohio since 2003

Eric Swalwell, U.S. Representative from California since 2013