Microsoft Exchange Team recently published a blog post outlining the timeline when the next version of On-Premises Exchange Server 2025 aka Exchange Server Subscription Edition (SE) will be available, and how you can prepare your organization to prepare for this upgrade journey.
As of today, most of the large Enterprise Customers still has Exchange Hybrid deployment in their environment, and the existing Exchange Server 2016 (Currently on Extended support) and Exchange Server 2019 will go completely out of support next year October 2025, so to stay supported with Hybrid deployment these Organizations need to start their upgrade plan asap and the article clearly explains the supported deployment model like with which version Co-existence is supported when RTM gets released and when CU1 gets released etc.
The blog post also answers most of the FAQs and upgrade guidance, if you are using Legacy Version of Exchange Server, it's now time to start reviewing your landscape and plan for the upgrade journey.
Access the Blog post here: Upgrading your organization from current versions to Exchange Server SE