I doubt they would put T2 in another paid DLC. That would be a bit crazy. I like what they did with Khitan but the level of effort to create those was probably enough that making a slight variation for another tier was not seen as cost effective. Funcom has been consistent with not making variations on T1, probably to encourage builders to move past that tier as soon as they can. T2 wood and stone brick are generic enough that they can stand in for a lot of styles.
I like the fact that the style blocks are in T3. It motivated me to build to that tier. If they are only making one tier of dlc blocks, they need to be T3. I welcome this. I tire of seeing black ice and reinforced stone buildings everywhere.