You are correct that the Cycles integration in Rhino 6 will be “limited” to Raytraced only. If you are looking to render at larger-than-viewport, custom, resolutions then you can use the ViewCaptureToClipboard and ViewCaptureToFile commands. Both know about Raytraced, you can specify a custom resolution and amount of passes. These commands will be a whole lot faster than Cycles for Rhino, too, so probably the better solution at the moment?
In the next public BETA there shouldn’t be a Cycles for Rhino -entry anymore, to stop confusing people.
Cycles for Rhino will return in the next WIP, which should be available at the same moment as Rhino 6 gets released.
Using CyclesForRhino.rhp from the beta/wip might still work in 6, but won’t be officially supported. That said, the same render engine is working when Raytraced and the ViewCapture commands are used, so you get the exact same results.