Just to clarify, what Ondra is referring to is just a 3ds Max native feature that only does what isolate selected (Alt+Q) does, but it happens only at rendertime. - This one is implemented already
The REAL render selected, that renders cutout of the selected objects but in the context of the rest of the scene is not yet implemented, but is planned to be.
The way Ondra said it is a little confusing. Render selected as in cutout of the selected object is not an advanced version of the render selected feature 3ds Max has in region to render dropdown menu. Those are two completely unrelated features for completely different purposes, that just share the naming for an unfortunate reason.
