Thanks. So it's a partial update with no Reaction but with better Datatypes , libraries etc?
Yes.
Why was a bug fix deemed necessary?
Huh? "Necessary"? Look, once again, I cannot tell you why you want the update or not. It was necessary because there are plenty of bugs or annoyances in the distribution, including the latest Os 3.9. For example the 4GB boot partition necessary with 3.9 is such an annoyance that will go away. The reboot will go away. The printer.device will work again.... there are plenty small bugs here and there.
The Vampire is the only fuel for Classic development so it's resonable to suspect Hyperion's rush is motivated by the Vampire and has caused them to instigate the update to the code for the new machines to increase cash flow at a difficult time for the company.
Oh my. Seriously... 3.1.4 is hardly on a rush. The whole thing is under development for 3 years now, so nobody was on a rush creating it. The original idea, put forward by Olaf back then, was to fix only seriously broken issues of 3.1 such as the HDToolbox which could not handle partitions or drives larger than 4GB. Actually, while at it, more and more components were reviewed and fixed. The whole thing is completely unrelated to the Vampire at all. It is a bugfix release that really went overboard because much more was touched than originally planned. 3.1.4 should have been a much smaller release in the beginning, but issue after issue appeared.
Is the plan to get third party developers to support OS3.1.4 going forwards instead of OS3.9?
I'm sorry, I really don't get your attitude. There is no "instead of". 3.1.4 is not incompatible to 3.9. So an application running on 3.1.4 will surely work on 3.9 as well. An application running on 3.9 that does not depend on reaction also works on 3.1.4. We'd love to include reaction, but we cannot.
How many copies would need to be sold for ongoing development?
No company would publically discuss its long term product and management strategy, not even with its developers. This is a management issue, not a development issue. I'm not a Hyperion employee, and even if I would, I wouldn't know the plans of the management. My best guess is that Hyperion doesn't know at this point either, and by best guess is that it would be rather stupid to stop a product line if it sells well. How well is "good enough" I can hardly tell and it is not on me to make this decision. It is a decision that will most likely be taken as soon as the plans for yet another release are on schedule. It's a little bit early to do that as even this one hasn't been rolled out completely (i.e. physical ROMs and disks).