I just discovered this thread. I was out of town. The Chiefs don't have anything to worry about.
Blackhorse and Sharjo and their team was successful with the Patent Board because they lined up evidence that 'Redskins' is a slur. They can't do that with Chief - in fact, in
the 'Proud to Be' ad, they list 'Chief' as one of the things they call themselves. Their stance would have to be that Native Americans should be erased from professional sports altogether, which will have an amazingly small number of supporters - as well it should. Pretending they don't exists won't be doing anyone any favors.
That's not to say they won't have any more affect. The article mentions that the Indians have scaled back the use of Chief Wahoo, as racist a caricature of an ethnic groups as I think there's ever been, and I wouldn't be surprised if you see it (him) replaced altogether within a few years. In danger are the habits of wearing headdresses, costumes, face paint, and doing the tomahawk chop - imagine if that was a spear-chucking chant or a pantomime of picking fruit or rice, and you'll get an idea of the zeal with which activists will go after its existence.
From the Chiefs perspective, they will handle this with PR rather than with lawyers. Beyond the Redskins name, other changes will come about as the result of social pressure, not legal action. The tomahawk chop is a good example; the Chiefs can stop leading it at the games, discourage its use, and then approach the activists from the perspective of having made real changes. If the activists then push for more, they'll come across as bullies and won't have public sympathy on their side.
So, in short: Chief Wahoo's days are numbered, and I wouldn't get too attached to the tomahawk chop at games. Otherwise, Chiefs is safe.