Microsoft has announced that Dynamics CRM version 2016 will be the last major version of Dynamics CRM to be supported by the connector.
I’m assuming that last major version means version 8 which include CRM 2016 with SP1 and SP2. Note that SP2 changes the branding to Dynamics 365.
The article above describes the supported scenarios. One thing to note is that NAV and AX incorporate a “new interoperability framework” to connect with CRM 2016 and later versions whereas GP and SL do not. This means, I think, that if you use Dynamics GP or Dynamics SL you cannot upgrade to version 9 (whatever that turns out to be) of Dynamics 365/CRM and still use the connector.
It seems that last major version meant 8.1 because this article, https://blogs.msdn.microsoft.com/crminthefield/2017/03/06/dynamics-365-monthly-update-february-2017/ confirms that 8.2 (Dynamics CRM renamed to Dynamics 365) is not supported for the connector. However, the article does describe an unsupported workaround.
There are of course, third-party connector options.