Earthsearch: Mindwarp: Chapter 1 CD is out of print!
It could simply be a coincidence, but the now sold out CD supply of all 3 chapters, does seem to intentionally coincide with today's first time release of Mindwarp 1-3 in digital format. The Chapter 1 CD with a £5 price indication (which now has been removed) did show this product to be available just days ago.
 Big Finish Talks Back: The Eighth Doctor Authors CD is out of print!
I'm curious - how do you learn about these things? Do you actually trawl through all the pages on a regular basis to see whether there has been any change, as that's got to take ages?!
I like to probe through some of the suspected ranges every few days. Today, I was double-checking to see if the Mindwarp: Chapter 1 CD is permanently sold out and noticed 2 releases listed above it that the Eighth Doctor Authors CD had gone out of print. Market prices and availability options of Doctor Who products is my thing.
As for the Main Range 51-100 CDs being eventually disclosed (probably during a UK morning when I'm asleep or at work) as out of print, I hope to see some different participants such as you, Mark, number13 et al. documenting the breaking news within this thread.
"Currently out of stock" CDs that probably will remain out of print.
[Jan 26-31, 2018] Big Finish Warehouse Clearance Sale aftermath:
 Dalek Empire: Invasion of the Daleks (1.1)
 Dalek Empire: The Human Factor (1.2)
 Dalek Empire: Dalek War (2.2)
 Dalek Empire: The Exterminators (3.1)
 Dalek Empire: The Healers (3.2)
 Dalek Empire: The Fearless (4.1)
 I, Davros: Purity (1.2)
 I, Davros: Corruption (1.3)
 I, Davros: Guilt (1.4)
 Rebecca's World - Journey to the Forbidden Planet
 Sarah Jane Smith: Comeback (1.1)
 Sarah Jane Smith: The Tao Connection (1.2)
 Sarah Jane Smith: Test of Nerve (1.3)
 Sarah Jane Smith: Ghost Town (1.4)
 Sarah Jane Smith: Buried Secrets (2.1)
 Sarah Jane Smith: Snow Blind (2.2)
 Sarah Jane Smith: Fatal Consequences (2.3)
 Sarah Jane Smith: Dreamland (2.4)
A possible candidate for re-press consideration would be the Comeback CD without any present option to download its story. Nick mentioned during the most recent podcast that Big Finish is having difficulty securing the digital rights for Comeback due to the noncompliance of Terrance Dick's agent. As for a CD release such as Rebecca's World, I have difficulty believing that it ever will be re-pressed. It's interesting to see that the I, Davros part 1 CD is still in stock.
Destiny of the Doctor: Vengeance of the Stones is now out of print on CD.
Another underrated series. I got my CDs from the much missed BBC Shop. Quite a novelty to have in the days before BF had the New Who licence. Hearing 11th Doctor nods in classic series stories was quite a thrill especially in that anniversary year where the wole geek culture of the UK seemed to be Doctor Who.