The Windows Server 2012/Internet Explorer 10 pairing is due to Microsoft's slightly odd handling of the transition from Windows 8 to 8.1, and 2012 to 2012 R2. There is no version of Internet Explorer 11 for Windows 8. However, for Windows 8, the Windows 8.1 update is essentially a service pack, and this includes Internet Explorer 11. Windows 8 and 8.1 have two years of "parallel" support, during which both receive updates. After that period, the (free) 8.1 update becomes mandatory anyway. The cut-off date for Windows 8.0 is also January 12, 2016.
Windows Server 2012 is the server counterpart to Windows 8 and ships with Internet Explorer 10. However, Windows Server 2012 R2, the counterpart to Windows 8.1, isn't treated like a service pack and isn't a free update (except for Software Assurance customers). Instead of two years of parallel support, both Windows Server 2012 and Windows Server 2012 R2 are supported all the way through 2023.
Unless Microsoft remedies this somehow (either by treating the server operating system the same way as the desktop operating system, or by releasing the new browser for the older operating system), Internet Explorer 10 will continue to be supported and updated.