I would assume that TN will support NTFSplus as it is being introduced in Linux.
(Full read write, permissions, etc.).
The perfect solution would allow encryption (veracrypt) so you can have a HD that a non Unix person could take to a Windows machine and only be able to get the data with the right password.
I think it’s very unwise to assume TN will ever “support”, in any official way, anything but ZFS. Whether they’ll make the effort to remove it from whatever version of Debian it lands in (or any future version of Debian that might form the basis for a future release of TrueNAS) is a separate question, but “support” is almost certainly a bridge too far.
This isn’t going to happen. At the very best, if this stuff gets into mainline Debian, TrueNAS will just leave it there, and you can ssh into the server and use this stuff manually at the command line, just like you can currently manually mount ext4-formatted drives and work with them on the command line. There’s no way they’re going to support this stuff in the GUI.