Plain and simple, I assume the names have been focus group tested, and "Ultra HD" tests substantially better than "4k". Not surprising really, and I think the article nails it:
Customer: What is that?
Salesmonkey: It's a 4k TV!
Customer: What does the 4k mean? Is that the price?
Salesmonkey: Ha hah, you wish! No, it's the TV resolution, which is 2160p, also defined as...
Customer: zzzzzz, I'm sorry, I must have nodded off there.
Or
Customer: What is that?
Salesmonkey: It's an Ultra HD TV!
Customer: Sweet, I like my things in ultra!
Still, until these beasts start coming down to just a bit more than normal HDTV prices, I don't think they're going anywhere. I think they'll have a similar transition rate between DVDs and BluRays, rather than VHS and DVDs for the same reasoning. The discernible quality difference between VHS and DVDs and standard definition TVs versus HDTVs is huge compared with the next leap up to BluRay and 4k TV. So I don't think many people will see a need to upgrade quickly. Plus, as being one of the people who spent $1,400 on a new TV a few years back, I'm in NO hurry to go buy the new shiny at 10x that cost. Let me get 10 years out of that thing (I hope), and I'll get back to you.