Mahogany continued as the typical outside ply on wrapped drums all through the 3 ply era (up to around 1977). In approx. 1968 they went to using maple exclusively on the interiors (although the occasional drums, often 18" floor toms, still had mahogany interiors) but the mahogany continued to be used on the exteriors under the wrap. Ludwig markets their Legacy maple/poplar/maple shells as being the same as this part of the 3 ply era but if you actually look at the drums nearly all (although not 100% of) the wrapped shells have the mahogany outer ply. Standard shells from this same time frame continued to mostly use the mahogany/poplar combination with not as much maple content.
I have heard that when Ludwig dropped the clear interiors for the Ganitone interiors that mahogany returned for at least some interiors. Hard to say as the Granitone hides things pretty well and I haven't owned too many of those to look at.
Regardless, mahogany content appears to have never really phased out completely until the changeover to the maple/poplar 6 ply shell design in the late 70's.