This has already started happening to me. For a variety of reasons I'm finding myself using my Acer Aspire Switch 11 more and my iPad and MBA less. (pretty surprising to me since my MBA is my best notebook ever)
It will be a while before I consider an S3 (it would cost me $750 for a Surface 3 configuration that I have with the Switch 11 @ $449) but there is growing interest for me to switch back to Windows... part of it has to do with available devices, other reasons have to do with how the environments are handled (including "forced" upgrade to iOS 8 on my iPad 4, "pressure" to upgrade to Yosemite on my MBA and iMac)
[Off-topic now] I am one of those that falls into an either or category but rarely both at the same time. I went with an iPad that I am still happy with for what I bought it for, which is primarily media consumption while on short trips with some social media and emailing (but not much typing) and flashcards (which work better on my tablet) - which is what the iPad was designed for. However I may be requiring a more functional laptop for contract work that is very close to having to be on-call, so even on short trips I might have to access a full laptop and thus upgrade (Remote Desktop on a touch device is nasty). If the new Macbook was out at the time I might have chosen it over the iPad..... When it comes to lightness and being thin - it is extremely important that the device be as least annoying as possible (remembering back to recovering from road warrior years and recovering from laptop induced injuries). I could carry an external keyboard with the iPad but it just seems like a bastardized solution - pulling out the tablet and keyboard / detatching keyboard putting it back in while in tablet mode or having the two pieces not tightly bound together while using it on my lap.... just feels like a clunky solution in regards to a device that is primarily a tablet.
I am still not ready to return to Windows as a primary operating system (I have 4 computers; 2008 Mac Pro; 2009 Mac Mini; 2014 Custom built Windows 7; 2013 Linux). With all the computers I prefer to use my Mac Pro (My Windows Machine is basically just sitting collecting hard drives - 11 x 3TB). I have installed and tried out Windows 10 for a few days, but I still feel.... uncomfortable with Windows.... and that is coming from using DOS/Windows machines since PC DOS 1.1.
The surface 3 tablet is intreging, and there are some interesting features like the pen (I do have a pen for my iPad for use with a whiteboard app only), but the keyboard add-on still feels like a cheap tackon -- not much different than keyboards for the iPad. I also don't care for touch interfaces on my computer, I find having my hand around the home keys with the mouse right next to it being more comfortable when using a computer for 8+ hours a day (mostly coding).