Part of why the previous attempt by the PTO to remove trademark protection was overturned was because the courts found that they did not have sufficient evidence to suggest that the word met the criteria for disparaging. There was not evidence that a significant enough portion of the potentialy affected population found the word in such a usage to be disparaging.
The question for the courts will essentially be whether or not there NOW is enough evidence to suggest this. To the opposition to the names credit, unlike last time they have the support of the National Congress of American Indians on their side stating that it is offensive and should be changed, and that group represents roughly 30% of native americans in the country. Now, it'd be incorrect to suggest that such a thing means 30% of native americans oppose the name but it is reasonble to say that the representatives for 30% of the population suggest it's offensive. Which may or may not ultimately be enough to rule that a large enough portion of the population feels that it's disparaging.
But the reason it wasn't previously was, in part, because there was no evidence that a significant portion of the Native American population found the use of "Redskins" by the Washington Redskins to be offensive.