For anyone looking to transition out of Sonar, given the unfortunate news, Studio One would be my #1 recommendation. It's a very nice DAW, lots of features, very flexible and straightforward, and relatively stable.
I found S1 pretty easy to pick up after using Sonar for years. You can map frequently-used key commands (like "s" to split an audio clip) to make the transition easier.
If you're thinking of running a Mac, I would also suggest taking a look at Logic.
And if you're seriously into the music production business and want to play with the big boys, Pro Tools is still king.
Cheers,
Eddie