I don't think you can draw any conclusions from what's in the past. Sony did what it had to do to get some lenses out there.

This bunch of lenses is an indication of future trends. Aside from the super zoom there are four DT lenses for APS-C with plastic mounts and one lens for full frame with a metal mount. I think it's reasonable to conclude that Sony is moving towards cheaper, plastic mounts for the DT range for APS-C.

I don't offer this as fact and it may be that longer (heavier) DT lenses may require a metal mount; can't say.