It sounds simple to me...
I have Sonar Platinum. That will now never change as I have entered into a contract with Cakewalk for them to provide updated core features and bug fixes as long as Cakewalk are around. Okay, they could go bust next year... Next month even, and that may have been the risk, but I think it's a small one.
Then, all the extras like plug-ins and synths, I can carry on using them as they are. If one get's revised and is offered as an upgrade, I'll consider at the time whether or not I want to upgrade that synth based on how often I use it and how much I like it.
Frankly, the way I use Sonar, the lifetime option was a fantastic opportunity for me to keep up to date with the main program, no longer having to keep my eye on upgrade options...