Will the show implement all the new rules for this season such as putting a guy on second in extra innings?
From the News section of the site:
"We at San Diego Studio could not be more excited for the start of the MLB season and what it means for MLB The Show 20. Like you, we've been waiting eagerly for the final details to be revealed, and with the start of the season, you will finally see some of your favorite content:
Roster updates are back! But to be more in line with the shorter more action packed season, roster attribute updates will now be weekly, compared to our usual bi-weekly updates.
Topps Now moments return! Relive the best plays, comebacks and walk-offs of the week to unlock Topps Now player rewards to use on your Diamond Dynasty squad.
Monthly Awards will crown the best performances from around the league each month in new Programs. Jump into missions and moments to earn the Lightning player of the month.
Play Now Live will mirror the new 60-game season schedule.
However, because the modifications to the official MLB rules and schedule were only finalized recently, we did not have the adequate time needed to properly implement those changes into MLB The Show 20 without risking damage to the current game modes and save files. The season length, rules, schedule, and roster sizes will remain as they would for a normal 162-game season. Extra innings and crowd sizes will also remain the same.
We remain committed to delivering you the most authentic baseball video game experience, and that includes the ongoing live content as teams chase a World Series title. Let’s play ball!"
TLDR version - No, they arent updating the game with any of the modified MLB rules for 2020 this year. Only the "Play Now Live" will be updated to adapt to the 60 game schedules.