As a first shot, I would say you shouldn't jump the gun on Carrara. Find out if it won't run on Yosemite first.

I deeply share your concern. The clock is ticking for us old C users up to the moment when our OS's shut us down.

I would also not rule out Vue. It has some of the most impressive rendering results out there and it isn't crazy expensive. I think blender is a great package and in some ways, it's ahead of C. In some ways it's not. I haven't been brought down to my knees far enough yet that I'm ready to devote a great amount of effort into a new program just yet.

I have given up on C ever having those wonderful outdoor superpowers that Vue and Terragen have so I'm going to invest in Terragen when it releases a new version this year.

As for modeling, there's wings and blender just as a start. I have also invested in Rhino as my backup plan when the clock runs out.

Based on cursory results and your art style, I would hazard that blender or cheetah3d would serve your interests. It's a pain to make the move but growing your skill set isn't a bad thing either.

Carrara isn't dead as long as we are still able to run it. Unfortunately, based on the limited information we have at our access, the odds of the end coming sooner than later are more likely than not.

-Kix