garageCube

I have a simple question: I have bought v3 back in 2019 for 2 seats. Many new features are not available in v3. The account page says something about 'preorder v6'. If I do this, will I immediately go from v3 to v5 while v6 is not out yet (it's in beta, I know), and v6 will be available once it's released?

My question is mainly about getting the v5 immediately when choosing 'preorder v6'.

Yes.
First, the only upgrade available at the moment (for any license) is the "v6 pre-order upgrade".
By doing so your license will be upgraded to MadMapper v6, and it will give you access to:
-MadMapper versions from v1 to v5
-the current v6 Beta
-the upcoming v6