I hate to be the bearer of bad news, but 532 and 542 will not return, hence the release samples of 532 II. 542 stocks remain because it was not as popular as 532 due to the very creamy base.
I purchased some Bergger CLF additive which is used to whiten the tone of "Silver Supreme." My intention was to see if it can whiten the base of the Foma papers but I've been working on other prints recently...will report back!
The paper base which was used by Kentmere and Foma is no longer in production. There is demand for these papers, a lot of people are coating their own paper, so I would like to see all the manufacturers club together and purchase some new paper surfaces.
Producing these papers on a large scale is tricky and not straighforward although Bergger seem to have been successful with their Silver Supreme using an Arches cotton rag paper. I've quizzed Linhof Studio who distribute Bergger in the UK to state if they know how long the paper will stay in production, but they have no information apart from "That it will continue."
To answer your question Mark, the Bergger paper is very lovely stuff, worth the expense? I would say yes as it is major hassle coating the paper yourself..I wouldn't have the time. It has gone up in price by 15% due to currency fluctuations. But you may waste a lot of paper producing lith prints.