Warden is still very busy. It's not a mistake to build it that many bus platforms. For Islington, Miway occupied the excess platforms. Wilson is the station with the extra terminal. Now they just use it as storage. I don't think it's consider wasted.
Mt Dennis would need that many bus bays anyways. As demand grows, many bus terminals like Kipling, Kennedy, Finch, STC, Lawrence West, Eglinton West and York Mills have became very crowded in rush hour. Even if the LRT was extended, only the 27, 32, 35, 170 and 195 bus bays will be freed. That assumes that a new bus terminal is built at Jane.
Even for the Spadina line extension, many buses will continue to operate to Downsview (Sheppard West) instead of the new Downsview Park.