>>So, what gives are there no more updates to the Mac version?
As far as I know, the MacOS 10.7 - 10.11 (Intel-based) last support date is 12/31/2016. So, there are no more updates to the Mac version(Unless otherwise notified).
Get Microsoft Silverlight : System Requirements
Support extends through the date shown in the table or through the support lifecycle of the underlying browser, whichever is shorter. As browsers and operating systems evolve, this table may be updated to reflect changes in browser or operating system support.
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