What a stupid mess this is!
It looks to me like S1pro is the knee-jerk response. As far as I can see the free version of S1 doesn't allow the import of VSTs, and I'd like to be assured all my investments work, but I assume they will. I have Cubase elements and never really felt comfortable with it. Plus there's Steinberg's charging for the 0.5 builds of their products.
Whilst Sonar could continue working, the risk of it collapsing half way through a half-finished album of work is too risky. I'm fortunately at a part of the cycle where I've just finished my most recent works. So it looks like a good time to jump ship.
The biggest pity is the possibility of this forum fragmenting. Presonus' forum looks moderately busy, but if a fraction of us from Sonar the forum invade them, they won't know what hit them!
See you on the other side, Dan!
Jerry