Anderton
A lot of people here claim to understand business and therefore say concepts like lifetime updates can't work. But there have already been proofs of concept of lifetime updates...last time I looked, Image-Line, Microsoft, Apple, and others are still in business. They make more from compelling add-ons than they made from OS updates. It's not rocket science.
Apple makes most of its money from hardware. It subsidises software in order to sell more hardware. I don't see how Gibson will drive physical sales from underpricing Sonar so I don't think this route makes sense.
Microsoft makes most of its money from licensed software which they replace over time - i.e. either the standard retail model or the rental/subscription/membership model. Sonar are moving away from that, so it's not a good comparison.
Image-Line's revenues are harder for me to find. But it seems reasonable to assume that this is a much closer match given the similarity of the software on offer. And what did we find with FL Studio? You get free lifetime upgrades, but very little has changed with the software in the 15 years or so I've been using it. Go dig up a video of 'Fruity Loops 3' and compare it to today's screenshots. They've basically added one new arrangement window and done a little bit of tinkering around the edges. And that's perfectly fine - why fix it if it isn't broken?
Unfortunately Sonar is not in quite as good a state. Yes, it's more capable than FL Studio, but it's also an order of magnitude more bugged and more unpredictable. I might retract that if the much vaunted 'ripple editing' and take-lane improvements deliver as promised, but in the long term Sonar needs a lot more fixing up than FL Studio does. But if people aren't typically paying for the core product but are paying for the add-ons - many of which will not be restricted to Sonar (again, see the Image-Line model) - there's going to continue to be this tension between working on fixes for people who've already paid and working on new things they can sell.
To be clear, I don't doubt Cakewalk's motives or think they're doing something underhand. I think they have a plan and I don't think that plan aligns with what I would want from the software, that's all. I might still opt in to the lifetime deal at some point just to get access to bug fixes for when I use existing projects, although I resent having to do that on a matter of principle.
Feel free to believe the negative people who have been consistently wrong in the past. Just hope they're not financial advisors 
I've been a negative person about the membership model. I feel I was right. It was a decent deal financially but my concern that they'd focus on shiny things for new customers and leave old stuff broken was borne out. The other aspect was the pendulum swinging from 'half the updates break something significant' in the early days to 'half the updates don't do anything significant' in the later months, so at least maybe they've learned from that.