According to Blu-ray.com, Optimum Home Entertainment will release Ran on Blu-ray on September 28. The UK release may be region-locked to Blu-ray region B.
A discussion topic at Blu-ray.com forums has some additional information, including the fact that the print will be the Studio Canal print that was used for the French HD-DVD release a few years back.
For more in formation about the availability of Kurosawa’s films on Blu-ray, see here.