The SharePoint Server 2016 RC is "mostly feature complete," according to Microsoft's blog post on its availability. Microsoft is still on track to make SharePoint Server 2016 generally available in the Spring of 2016, today's post also confirmed.
SharePoint Server 2016 will include an ongoing capability to host InfoPath Forms Services. InfoPath Forms Services on SharePoint 2016 will be supported for the duration of SharePoint 2016's support lifecycle.
InfoPath Forms Services on Office 365 will continue to be supported.
InfoPath 2013 and SharePoint Designer 2013 will be the last versions of those products. SharePoint Designer is not being re-released with SharePoint Server 2016, although we will continue to support custom workflows built with SharePoint Designer and hosted on SharePoint Server 2016 and Office 365.
Support for InfoPath 2013 and SharePoint Designer 2013 will match the support lifecycle for SharePoint Server 2016, running until 2026.