Actually it's PhotoKit Sharpener by Pixel Genius, David.
Adobe are quite keen to have 3rd party involvement and to this end introduced an SDK with Version 1.3. Keeping an SDK active means writing the program in a way that it's easy to hook into. Of course doing this adds to the time needed to create and test code.
So the SDK is being expanded in stages. I'm sure with the release of V2.' we'll see added functionality in the SDK, but I suspect that full blown module style plugins are a way off yet. I could be wrong, but I've seen no one announcing such development. In fact PT Lens was recently released in an External Editor form for Lightroom, rather than a 'Plugin'.
The team isn't particularly large, so there is a finite amount of time to do things in.
We saw the basis of Local corrections in the beta, this took a lot of work to get to this rough stage, and I'm sure that it's been refined further. Still, it's time consuming work.
The day will come and sooner rather than later, but from rumblings on the net and other forums, I don't think we'll see what you want just yet. Of course, I'm get things as wrong as anyone, so this is all speculation.