Predictions for NewCo aka Ballmer, Barnes and Noble
1) B&N will pay royalties on their Android Nook... for as long as they keep making it, which I expect is at most months. I.e., this will cost B&N virtually nothing, and MS is certainly paying them a lot more than those royalties will be worth, anyway.
2) The obvious "Duh" item: a new Nook Color based on Windows 8 RT will be out for Christmas, most likely a repurposing of their existing hardware with W8RT, possibly with minor spec upgrades to suit W8RT. The Android Nook Color will disappear. Not sure what will happen to the e-ink version, since I doubt W8RT will run with a grayscale e-ink screen, even if it has touch. It may stay an embedded Android version, or MS may cook up an embedded Win8 specially for this (i.e. a WinCE replacement for embedded applications).
3) Less obvious: college bookstores run by NewCo will suddenly stop selling Apple products. Win 8 ultrabooks and tablets will get pushed heavily. MS is losing significantly at the crucial college level where students buy their first computers. Owning the college store will help stem this hemorrhage, especially if there are no iPads there to buy.
4) Maybe: NewCo will push/bribe textbook publishers and/or college faculty to produce/require textbooks *exclusively* available on the new Win8 Nook. If students have to either buy physical texts or another reading device, they may forgo buying an iPad that won't be able to handle their texts.
5) Remote possibility: the iOS and Mac Nook apps will disappear, or more likely just get heavily ignored for updates. This would be semi-bad for the book side of the business, so it may get heavy pushback from the bibliophiles in NewCo. I definitely expect the Nook apps to be disadvantaged vs. the shiny new (and MS-written/subsidized) Win 8 Nook app, which will very likely get all new features first.
6) Probable: the Nook W8RT will get streaming media content via MS's Xbox deals, and probably tie into MS's cloud services. Competing media apps and apps for other cloud services (Google, Dropbox, Amazon) may not appear/be allowed. Same for apps that reproduce MS Office functionality (a college version of the Nook W8RT with Office RT on it seems probable). It's entirely possible these sort of restrictions won't appear initially, in order to gain market traction with the Win 8 Nook first. (see also Kindle Fire support for Hulu and Netflix... for now).
I also expect if Apple introduces a smaller "iPad Reader" model near the Kindle Fire/Nook Color price point (I'd actually expect $299, or less likely $249), the Nook W8RT will probably be stillborn unless MS can swing some muscle to deny content to the iPad, especially in the college market, or they can price it below $150, which seems unlikely without selling it at a loss (which MS is probably fine with if it gets Win8 RT some tablet traction).