Proof you know nothing of which you speak in terms of what's involved during development.
I'm not saying it'd actually take them 40 years (my guess is he was exagerating), but to say that's all that's involved is utter hogwash. To model, texture, light and animate an environment (especially at the ridiculous expectation of detail that people have these days) requires an immense amount of time, skill and talent on behalf of not only the artists and programmers but also the directors and managers.
And it certainly doesn't just involve texturing and modelling (which takes a very long time as it is), but you're also looking at character rigging (a very technical and creative process which is time consuming), character animation (this is probably the most time consuming thing from an art perspective; an animation studio that did Saturday morning cartoons that I knew a lot about did about 20 seconds of animation per week) and post-processing things like particles and lighting which are a whole other beast in themselves. I won't even get into the technical/coding side of things, where optimisation is such a huge aspect.
Basically, to get a high production project done you're looking at spending about 50,000,000USD and about 3-5 years of your time. These figures are nothing to be scoffed at, and you're in a huge amount of risk if things go wrong. These huge companies do know what they're doing; they do know what talent and skills to hire for their company. They aren't slack, they aren't stupid, etc. etc. They are just weighing up the risks involved and the extremely high expectations the industry and fanbase expect from such a project.
I am honestly not surprised it'd take longer than any project they've done thus far, but I am really guessing that the 30-40 years statement is completely exagerated.
Edit: Btw, that's just talking about the production phase. Pre-production and post-production stuff adds on probably double or tripple the time.