Is it possible to create a WPF plug-in dll directly without hosting it inside a WinForms user control element host? If so, an example would be appreciated.

The answer is no.

There is one exception: In MIP SDK 2017 R1 a SettingsPanelPlugin was introduced and the SCSettingsPanel sample added to illustrate how a larger WPF configuration oriented user control can be created.

Note. It is on the wish-list to introduce WPF plug-ins in general to MIP SDK 2017 R3 which is planned to release before the end of the year.

Is there a release date for MIP SDK 2017 R3 ?

No. It will release together with the XProtect products R3 version, but for now there is no date planned.