To the the best of my knowledge, there are no plans to offer a Platinum edition CTS or CTS-V. I would assume this is maily becuase the CTS/CTS-V already have the had cut and sewn leather dash and doors that are a big part of the Platinum upgrade. I realize that with the Platinum editions you also get upgraded leather, headliner (suede), and wood trim (decorative inlays) that are not offered in the CTS.
What might be of some help though is a little known fact that Cadillac will customize any of there cars for the customer to their specs. I am not completely sure how to go about it, but for a price, you can get any Cadillac equipped the way you want it. You have to pay a premium for it, and I am not sure how the current GM situation will effect ordering one. I would think that going through this process would add at least 4 weeks to your build time, as the car has to be custom made. I am not sure if Tony or Scott, both Cadillac sale people, know any more about this than I do, but you might inquire with Cadillac directly via phone. The last car I know of that they built, not to say there aren't others, was a 2007 XLR-V with White Diamond Paint upgraded Leather, and I believe the 468hp version of the Northstar. Note the standard XLR-V had the 443hp Northstar, and was not offered with any other colors besides Red, Black, and Silver.
I hope this is of some help.