Pour les trucs vendus par microsoft, ils sont visiblement transférés oui. Voici la réponse officielle :
Owned MSFS 2020 Content that has been Upgraded* for MSFS 2024
For content you already purchased in MSFS 2020, upgrades to Microsoft-produced content (e.g. Reno Air Races, Local Legends, Famous Flyers, Expert Series) will be free to you.
For content you already purchased in MSFS 2020, upgrades to all other (non-Microsoft) developers’ content will have two potential options based on each developer’s discretion:
The developer can make the upgrade free.
The developer can choose to charge a fee for the upgrade.