To me, it's a classic. I love the album, my favorite Tech album. Everything on it has meaning. It's deep, it has a theme... Not many albums, especially in hip hop, have that much relevance.
But, on a mainstream level it's not a classic. When you talk about classic albums to most rap fans, this won't pop up. Tech fans will mention it, but that's only about 300,000 people.
So, it's not a classic on the level of All Eyez on Me, or Ready 2 Die, or anything like that, but I believe it's a classic for Tech's audience, but not in a general hip hop level. People have to listen to it to be a classic.