The think-tanks come and go. In the late 60s the Oz military decided that the old method of starting on the piston Winjeel and then finishing on the Vampire should be replaced with all-through jet training on the Macchi. It was tried, but they found it was an expensive way to be weeding out the duds, so they went back to Winjeel / Macchi and later CT4 / Macchi. Now it will be 2 types of PC9 and PC12 I think.
For rotary it was all Huey, then it became Squirrel / Huey, then Squirrel / Kiowa / Blackhawk and now it will be all twin via the EC135 route. Again, they think that pilots will always be on twins, so why not go all the way. Wait a while, and perhaps a single for basic will creep back in.