Will Nokia Lumia 2520 get Start button (and Windows 10)?

Windows 10 Technical Preview (for x86) is out there. Go and get yours! But what about ARM-based devices? Microsoft answers:

"@HardwareNerd Right now tech preview is for x86 PCs. ARM devices and phones, not 'til well into 2015.
— joebelfiore (@joebelfiore) October 1, 2014"

Let's say I'll buy a used Nokia Lumia 2520 -tablet next summer 2015. It won't be too expensive, still in good condition and some guarantee possibly left. So my questions are: will there be a version of Windows 10 for ARM-based tablets? If, will there be a Start-button or Windows 8.1 -styled Start Screen instead? Will I receive Office 2016 (touch version) for free for Lumia 2520 (I doubt)?

Microsoft says Start button is available only for PC users. Tablets will continue the same way as with Windows 8.1 because of the touch screen. Honestly, I'm not interested in Start buttons at all. Only want to know and am looking for answers. Let's hope Microsoft tells something soon. Until then let the price of a used Lumia 2520 sink!

Windows 10 with Start button on my Dell PC