Only if you've got all Golds - the point I believe he was making was that if you got a title for one Gold, people may try really hard for that one gold, get it and then proceed to realize that they both enjoy challenge modes and want to go for all golds to get the armor set - boom, hesitant people participate and challenge modes become even more of a success.
That said, I feel like the titles will probably be permanent because someone who desperately wants one of them (Darkmaster and Flameweaver I see being the most popular) will try to find some extremely cheap way to get an outrageously low time via some method that's not exactly practical to organize or some such now to just get gold (but not the goldest gold, :P) for the armor set and thus will be unbeatable unless someone repeats the tactic and shaves .01 or something off the time.
EDIT FOR CLARITY BEFORE SOMEONE GETS ALL EJROAKLJSDJ ON ME
I'm not saying Blizzard will make the titles permanent, I'm saying some of them will be effectively permanent because of the above-described cheesing someone will pull to keep the title they want the most, assuming said-cheesing can be done.