Forum: anybody's guess...
Transfer: I'm planning to go through important projects and render everything to individual tracks that are all full-length, i.e. left-justified, for easiest trasfer to a different mixing environment in case that becomes necessary or interesting. That's relatively easy and can be semi-automated.
For more control, if it seems useful, I will then make MIDI tracks for any soft-synths involved, and save those plus plugin presets in the project folder, with accompanying notes. Same for any FX that I might want to be able to change settings on at a later date. That's a fair bit more work and cannot really be automated at all, so I would only do that if/when a project seems important enough to justify it.
Haven't decided what I might be importing things into yet, but that's just future-proofing even if I decide to continue working in Sonar for the foreseeable future, which is certainly one option...