I'm interested to see how this pans out - the reality is, the lions share of the costs for animated features have nothing to do with rendering. I'm concerned they are buying the worst of both worlds with this approach: they still have to create good looking art assets, they still need to animated them well, but they are further constrained by the confines of what they can do in a realtime engine, with a toolchain that is not optimized for this type of work.
I do think that there is a ton to be gained from tightly coupled previs pipelines that don't incur rendering overhead. Ideally the artists should be able to see what they are working on in a form that is as close to the final render as possible, but without the wait. Systems that can offer this with low overhead cut down on the amount of time the artists need to get the results they want tremendously, especially in situations where your team isn't big enough to have modeling, texturing, animation, fx and lighting departments that are completely siloed.
That's not quite true - render time still is very important, even for the biggest studios like ILM/SPI/Dreamworks with the biggest renderfarms.
However, yeah, artist time is more costly, and recently GI pathtracing raytracers have made huge inroads in the VFX industry due to the fact that lookdev/lighting configuration is much quicker for the artists due to being physically-based, so you get very realistic lighting without faking it with AO or virtual lights.
It definitely speeds the iterative process up when the artists can see how the scenes looks on their workstation without kicking it off to the renderfarm and waiting 4 hours for a render to come back.
With Arnold or VRay, it's possible to get a very fast 3/4-bounce GI solution with heavy geometry and textures in a matter of minutes.
You have a point, however in regards to render times I was more speaking to films in this budget range. Big studios have custom toolchains, and do everything in-house, rendering included. If you are using non-proprietary 3D software, there are rendering services at your disposal that are often pretty reasonably priced.
I do think that there is a ton to be gained from tightly coupled previs pipelines that don't incur rendering overhead. Ideally the artists should be able to see what they are working on in a form that is as close to the final render as possible, but without the wait. Systems that can offer this with low overhead cut down on the amount of time the artists need to get the results they want tremendously, especially in situations where your team isn't big enough to have modeling, texturing, animation, fx and lighting departments that are completely siloed.