The folks of IHS iSuppli have told CNET that the production of displays for the Retina iPad Mini is going pretty much the same as the production of the first iPad Mini panels. Volumes are described as similar to those seen in Q4 2012.
The first gen iPad Mini was launched in November last year, which makes me think we could see a similar time frame for the launch of the new model this year. The rumored Retina version of the slate is expected to rely on a 7.9 inch panel with a resolution of 2048 x 1536 pixels, the same as the one of the iPad 4 Retina screen.
Because the display is smaller, pixel density will increase from 264 PPI on the iPad 4 to about 324 ppi on the new Mini. That would be about the same density of the Nexus 7 gen 2 model, that offers 323 ppi, the highest achieved on a tablet till now. LG Display is expected to supply the bulk of the panels for the Mini Retina, at least initially, but Sharp will also play a part in this project.