I wonder what major advantages there are to update the GS7 to Nougat...many of the added features don't apply to the GS7 because of TouchWiz. The major feature that'd apply across the board is native VR support (but doesn't the GS7 ship with VR support even in Marshmallow?). I've experimented with a Galaxy Note 4, and even in KitKat, it already integrated many of the Lollipop features prior to receiving the update.
If you're impatient, you can probably flash your GS7 with an OTA or stock firmware from an alternative software channel. Good things come to those who wait.
As much as everyone gets rowdy over OTA's, if software updates are what's most important to you, get a Nexus/Pixel device. If you are a Samsung fan, then you could order the phone from manufacturer or get them on promo through carrier, and wait for OTA's through manufacturer/carrier.
Given OP's choice of handset, it suggests that rocking a Samsung is far more important than using the latest update. Rumour has it that Nougat will be the last major update for the GS7 - link: http://www.androidguys.com/2016/03/14/consider-this-your-latest-s7-purchase-may-only-get-you-one-maj...
You got the phone with Marshmallow, expect it to work with Marshmallow. Granted, most flagship phones get two major updates. Looks like Samsung is hoping that you'll upgrade your handset sooner by slacking off in their software engineering.