Drew,
Obviously we do not have an 'insider' financial info on most of the philatelic companies (few are public companies with published annual reports) so we are left with industry observations and opinions.
My opinion is that the philatelic publishing industry is not immune to the sweeping changes the rest of the world has experience with the advent of the internet. I also think that the traditional philatelic publishing industry would follow the same trends as the larger general publishing industry which it is a part of.
Moving from opinion, here is one publishing industry trend that can be described as fact. According to the Bureau of Labor Statistics 2016 report,
Quote:
Few industries have been affected by the digital or information age as much as newspapers and other traditional publishing industries (books, magazines, etc.). In June 1990, there were nearly 458,000 people employed in the newspaper publishing industry; by March 2016, that figure had fallen to about 183,000, a decline of almost 60 percent.
They go on to say,
Quote:
"Over the same period, employment in Internet publishing and broadcasting rose from about 30,000 to nearly 198,000.
If you look at the numbers for tradition print publishers, the trend is clearly down. Here is the trend for printed newspaper circulation

The trend for printed non-fiction publishers is not any better; sales down 23% in the years from 2004 - 2014

Another metric for traditional print media industry is the decline in periodical advertising spending.

I guess folks can speculate that the philatelic publishers are some kind of outlier and are not effected by the same trends as the rest of the print industry; time will certainly tell.
Don
Edit; We can actually take a closer look at one publically traded philatelic publisher; Stanley Gibbons.
According to their 2016 Annual Report (all the standard warnings about Annual reports apply, companies may manipulate the numbers to influence shareholders).
SG Publishing and Philatelic Accessories profits were down 1/2 million pounds or 59% in 2016. This is due to a huge drop in gross margins that followed their decision to outsource distribution of Their catalogues, albums and accessories.
Why did they start outsourcing distribution?
To lower their operating costs; SG dropped their catalogues, albums and accessories inventory from £1.2m at 31 March 2015 to £0.3m at 31 March 2016.
Outsourcing their distribution and cutting inventory does not sound like a healthy traditional philatelic publishing segment to me.