According to the
Microsoft Learning Retired Exams page:
Exams scheduled to retire
Find exams scheduled to be retired in the next 12 months, listed by technology. (The information that follows is subject to change.)
[...]
Windows Server
[TH][/TH]
[TH]Exam[/TH]
Retiring on July 31, 2017
70-640: TS: Windows Server 2008 Active Directory, Configuring70-642: TS: Windows Server 2008 Network Infrastructure, Configuring70-646: Pro: Windows Server 2008, Server Administrator98-365: Windows Server Administration Fundamentals
Mind you, this doesn't mean that Windows Server 2008 R2 itself is being retired, this is just an announcement for the certification exams. The server product still continues to be supported by Microsoft without any announcement to the contrary, as of this writing.