As Bapu points out, anyone who thought they'd be getting free updates in 5-10 years was whistling up a Dixie tree for a free lunch. Fruity Loops made one-time purchases work for about 5 years, but I have the feeling it was a much lower-cost operation than Cake, which has a real staff. I thought that would last a little longer.
I dont' think Gibson was scamming us (except the Momentum thing - which means they have to keep a server open for that for a year). I think Gibson made a go of it and had some "consultants" say if you buy SONAR and we do this promotion we think we can sell X units and pay back Roland and then on to Moscow and conquer the DAW world. Well, it didn't work and Gibson has made a few other mistakes like that so has no cash to fall back on. But simply shut down a product?
I can't see them (or anyone) letting Cake just die - it still has value. Just looking at the forums there are plenty of people that would buy or upgrade SONAR, and the forumites are a small percentage of buyers, and a small percentage of current users. There are hundreds and thousands of users able and willing to shell out $100-or more a year. That is a lot of cash to leave on the table. Not enough to staff a full company, but enough for a couple of developers.
As for the rest - I upgraded Vegas through Majix. Now it doesn't work, but Vegas 7 works fine on my win 7 (along w/ SONAR). So it ain't the end of the world. Not great news, but you are good to go for the next few years w/ SONAR, tho I wouldn't open a studio using it after today.