NSX-T 3.0 is out, with many improvements to 2.5.1 and tighter integration with the recently released vSphere 7. Look for a write-up later this month!
See the blog post announcing it: https://blogs.vmware.com/networkvirtualization/2020/04/nsx-t-3-0.html/
I expect an update to the NSX-T Design Guide in the next month or 2, you can find it here: https://communities.vmware.com/docs/DOC-37591