For words on the topic from Robin Thorn himself, please see...
https://thorncyclesforum.co.uk/index.php?topic=15020.msg113316#msg113316
Best, Dan.
Thanks for popping in that Link, Dan. It's exactly what I was referring to above - and very appropriate for this thread.
The core of Robin's explanation is:
"The current PLAN is a new model with flexibility of the Nomad mk3, the tubing of the audax mk4 and be very similar in function to the Mercury. This is a plan, there's no model name, price point or time frame."
Adding that he didn't have anything else to contribute.
So reading closely, my comment above that the new model would be a combination Nomad-Mercury was a little misleading. Rather, it sounds like the shop has in mind something rather like the Merc in performance but with more flexibility in how it is specified.
Regarding @Andyb1's query on why change the Merc Mk 3 at all, I think that is a good question. They've got a classic design amd very possibly could leave it alone.
Against that is a comment I picked up from Sarah when ordering mine, that when ordering a production run of frames from their builder in Taiwan the number required would satisfy about five years' worth of sales. (To hold down the cost per piece, compete with orders from other firms, etc, I'm guessing.)
And then when they order, they go into a queue and the frames come out a year or so later.
So if they were to order a new batch of Mercuries, they'd have to be pretty confident the bikes would still be in demand at the predicted price point five years later, when the investment would be starting to turn a profit, and not a pile of metal hanging in a warehouse that could be sold only at a discount because even touring cyclists had latched on to new fashions.
Re the carbon fork: from photos quite a few of the earlier Mercuries were sold this way. The main reason you'd do it now would be to offer a disc-brake front end that retained a bit more springiness than Thorn's heavy steel disc fork delivers.
I see the shift to discs as a significant risk for Thorn. Most consumers won't understand the downside of a disc at the front, and will assume Thorn is simply old-fashioned in recommending a rim brake. Eventually it will get hard even to supply a good rim brake.