[PaulDavisThe1st]

But there are (at least) 12-20 DAWs, each with their own (internal) abstraction designs. It's bad enough having to write (or being able to write) plugins for:

   AAX, VST, AU, LV2 (at least)

Now you'd be talking about 12-20+ different "plugin APIs". That's not going to fly.

[lavabiopsy]

As per your other comment, it seems things are already going in that direction, if developers are treating their plugins as being written in a format that could be described as "AU that is compatible with Logic but nothing else" or something like that (substitute for any format/DAW combination that the developer wants). So I would say that in a way it has already flown regardless of how we feel about it.