The steam (and also Xbox store. I'd imagine PS4 one is the same) store gives a couple of details.
o NEW MYTEAM MODE - An immersive driving game, players can now create their own F1® team.
* Create a driver, then choose a sponsor, an engine supplier, hire a teammate and compete as the 11th team on the grid.
* Build facilities and develop the team over time and drive to the top.
o NEW - Two new races: Hanoi Circuit and Circuit Zandvoort. NEW - Split-screen racing.
o NEW - Casual race options for more relaxed racing.
o NEW - Shorter season-length options: 10, 16 or full 22 race options.
o All the official teams, the drivers and circuits from the 2020 Formula One World Championship™.
o Acclaimed ten-year career mode.
o Formula 2™, the ultimate training ground for F1®, is also included, now with new half or full season options and 2019 and 2020* season content.
o x16 classic F1® cars from 1988-2010.
o Esports - in-game area for the online qualification events, latest news and even watch the new F1® Esports Challenger and Pro Series races.
o More ways to race: Time Trial, Grand Prix™ Mode, Championships and relive your glory with saveable automated highlights.
o Compete online in Multiplayer: Ranked and Unranked races, Leagues, Customisable Liveries and Weekly Events.
*Online connection required to download the final teams’ 2020 cars (as applicable) and the F2™ 2020 season content post-launch.
Looks like the 1970s cars are gone. Not a massive shame for me as I wasn't too fond of them. Still, all the classic cars have been relatively under-utilised compared to F1 2013 which had actual classic circuits and suitable drivers in them.
Confirmation that the 2020 cars will get updated, as well as the 2020 F2 content.