Yeah, sometime, when the time is right
Sorry, I don't buy that New York just isn't a rock town, never have. But it is always an open question about how many rock stations the market will demand given limited frequency space in a market like New York, competing demands for other formats, or what type of rock format should be aired.
Z-100's hybrid of modern rock and CHR was right for the times, but it doesn't seem right for 2006.
Rock has lost a lot of listeners to hiphop nationally, especially young male listeners. Also, the most interesting rock now doesn't seem (to me at least) to have such great broad market appeal as it did in the past. (My $0.02, feel free to disagree.) Maybe commercial (terrestrial) radio and rock are just sort of diverging, at least for the time being?
Look at how CHR is doing these days -- pretty well, overall. Ten years ago some people were saying Top 40's days were over, and I can recall a few major markets that just didn't have any CHR outlets. Actually, I think San Francisco still doesn't, but it has at various times since the mid-90s (e.g. Z95.7) Also, CHR stations in some markets (like Philly) seem to be struggling. But overall, CHR came back, thanks in part to a broader audience for hiphop, boy bands, maybe even American Idol, and lots and lots of successful celeb-singers like Britney, Beyonce, Christina, Kelly Clarkson, Jessica Simpson, etc.
Does any of this apply to rock? I think so. In terms of its commercial appeal, I'd be willing to predict a resurgence, but it would be a mistake to map commercial rock radio's future by going back to the past.