Ramon, I'm in the situation that is like your friend's. I am still planning to go 5d mkiii - it's the camera I will use for many years in the future, it's one hell of a camera (well, according to early reviews). The problem I face is that I'll have to adapt realizing that I will be carrying 4k$ worth of equipment around. I think that's the only trouble really. If he can afford it and feels comfortable carrying such expensive equipment around, he should definitely get it.
5d mk III >>> 30D
This is a very good point, but the recuring cost of an insurance policy should be considered as well.
Also, your friend should consider the potential cost of computer and storage upgrades that may be needed. If he/she was processing 30d photos with a 3 or 4 year old computer, they aren't going to be very happy when it takes 30 seconds to load a single 5diii image! Data storage/backup needs are going to go up by 3-4x too.