Meanwhile over a year has passed and PDF/X-4 still remains a somewhat obscure file format. It is quite logical that the adoption of a new standard takes time though.
Those looking for an overview of PDF/X-4 might be interesting in my write-up at http://www.prepressure.com/pdf/basics/pdfx-4
I don't doubt that PDF/X-4 will be important and frequently used in the long run. But as you point out yourself, companies are only now starting to look into it. GWG's next standard will be based it. PDF/VT isn't finalised yet. Even when these standards are released, there will still be a bit of lag before the industry picks this up: vendors have to make software that can handle the standards, customers have to purchase these systems, trials have to be run,...
I think that at this point in time PDF/X-4 is still obscure.
I did not say that companies are only now beginning to look at it (PDF/X-4). Those are your words!
When the printer and publication companies I mentioned are in production with PDF/X-4, that is not beginning to look.
In this case, I will humbly suggest that obscurity is more a matter of your frame of mind with regards to this standard than reality. Those in print production who continue to be in denial of reliable 21st century print workflows will be the ones who become obscure, otherewise known as "out of business!"
Whether 'rolling out' equals 'looking into' or 'in actual use' is a question of semantics and one's view of marketing speak :-)
I'll let Google tell us how much interest there is in PDF/X-4. If it is 'that hot', many people must be looking for information about it. According to the Google Adwords tools, the monthly global search volume on the (exact) keyword 'pdf/x-4' is 480. 'pdf/x-3' scores the same. For 'pdf/x-1a' it is 880 and for 'pdf/x' it is 3600. 'pdf' scores 1830000.
We both agree that PDF/X-4 is the way to go. That is more important or interesting than the question whether it is happening now or 'real soon now'.