I've learned that んですか can be used to check an educated guess, as in:
(upon seeing someone dragging a piece of luggage)
ねえ、旅行するんですか。 Hey, you're going to travel, aren't you?
I've also learned that でしょう can be used to express an educated guess, the validity of which can be checked with ね — or self-doubted by か or a rising tone:
雨が ふるでしょう。 It's probably going to rain.
雨が ふるでしょうね。 It's probably going to rain, isn't it?
雨が ふるでしょうか。 I wonder if it's going to rain?
What I want to ask is if んでしょう or んでしょうか can be used, and if so, what their connotations are. Google shows they exist, but are they part of standard Japanese?