I can upgrade to Carrara Studio (with Amapi 5) for $149 NOW or wait 2-3 months and get Rhino (through Renderosity) for $570 - if the price doesn't change. Any recommendations? Thanks.

I have both, and am currently going through a bunch of tutorials for rhino, the learning curve is fairly steep, but so far it's incredible. Get Carrara, it's got a great render engine, between carrara and rhino theres nothing you couldn't model. I would get carrara studio now, and buy rhino when you can. Rhino doesn't have a renderer like carrara, but you will get flamingo with it, but it's not as beautiful as carrara's renders.

I curently have both. Your best bet is to do the same, modelling in rhino is superior in just about every way, and if you can learn to use it, then i say get it. (Also if you have autocad experience then definitely go for it). As for carrara, its far superior renderer can make anything you've made in rhino look like a dream. Exporting in 3d studio format is the best method i've found. Good luck!