The lifetime offer on the face of it seems okay to me. I agree with the OP that once the OSX version is rolling out the door with paid for versions, the goalposts will be moved. The lifetime upgrades will be exactly that, for the lifetime of Platinum.
There will be another momentous announcement of a brand new Sonar (or whatever it is to be called) melding everything that has gone before into a new hybrid product. And yes, this will require folks signing up for, yes, a new SUBSCRIPTION model...there will be no lifetime upgrade offers with that!
Remember as "folksy" as the people who work for Gibson try to be, the company is STILL a company and have no real regard for the personal happiness of people who licence the software. They gamble on the premise that possibly up to 95% of existing Sonar owners are so committed to the software (and not just becasue of "liking it" but also because there would be a huge upheaval in modifying personal music data to change DAW's) that they will simply accept the new "model" albeit with lots of grumbling (although there will always be apologists) and after a time it will all settle down and Gibson will go on its merry way.
Politicians count on it all the time, the publics' short (extremely short) attention span for remembering what decisions were made and how those decisions adversly affected lives. Corporations, companies, Governments, they all operate on the same premise.
Personally I bought the lifetime upgrade as I figure it will take approx two years to get an OSX version fully ready for market
(but who knows maybe Gibson have been developing OSX versions even while denying it will ever happen??? so my guess could be way off)......this cost me $146 (Im in Oz) which is a lot cheaper than paying for two more years worth of subs.
I make no criticism of Gibson - business is business and were I in its position I might do the same. However I would appreciate them not trying to be so "buddy-buddy" about it, as if all of us (users) and all of them were somehow part of one big "family" all looking out for each other.
As always, jmo