Nikon Lens AF-S NIKKOR 50mm F/1.8G?

Does anyone know when this lens will be back in stock?

No idea…
I keep track of things Nikon related at this web site.
http://nikonrumors.com/

At present many very popular Nikon, Canon and Sony products are in short supply due to the earthquake and tsunami last year in Japan and then the devastating floods later in Thailand.

Production is rampping up, but it will still be a while before all products will be available, especially the most popular ones.

The good new is that the new production facilities will be able to produce even higher quality products and at a faster manufacturing rate