This is a subject I can definitely comment on.
I started buying blog domains in 2002 in earnest; I started buying vlog and vodcast domain in earnest in late 2004 and 2005.
In each category I own what would be considered probably one of the best sets of blog, vlog, and vodcast domains you could imagine since I started buying before anyone else. As far as I could tell I was the first real hardcore buyer. I did miss out being first on podcasts, but still own a lot of them.
Here is what I learned..... blog domains were considered silly in 2002 and nobody wanted them.... generic + blog + .com . I got a lot of laughs about buying those.
Vlogs and Vodcasts still are kinda' considered silly terms, but "podcasting" has caught on a little bit.
Whether the terms vlogs and vodcasts will catch on or not is specualtion. I think they proabably will not catch on (even though I just renewed a bunch), and will be considered more of technical terms that some developers use instead of the mass population. Anyone can start a blog in five minutes. Does anyone in the public really know how to make a vlog, vodcast, or podcast, and like one poster said above..... they probably would just call it a blog anyhow.
My highest traffic vlog domain had 47 visitors in the last 365 days, my best earner comes in at $1.09 for the last 365 days..... if that tells you how far we are still away from mass recognition of the term, and these are on vlog domains of which I can't imagine owning any better.