Update : Windows 10

[Yuhaney]

Wouldn't surprise me even if it was true.

[Mudbill]

I highly doubt they will stop supporting Windows 8.1 in a year. Windows XP had its end of support last year, about April 2014, nearly 13 years after its release. 8.1 is only, what, 2 years ago?

Aside from that, anyone who installs Windows 10 now might want to look at this setting:
Unless you explicitly tell Windows not to, it will share its files with anyone on the Internet. This includes Windows installations and Windows updates to anyone who can make use of your bandwidth. This setting is on by default and is there to speed up downloads by using nearby people's broadband, almost exactly like a bittorrent system.

If you have a slow connection to the Internet, or prefer not to share files with others due to privacy concerns, thoroughly look through the settings. This particular one is under Advanced Settings of Windows Update.

Source

[Catalyst]

I was reading on Russian Hi-tech forum that W10 users will deal with graphic drivers compatibility, that will slow down the system, on currently supported graphic platforms W10 got only 20 % of power. I think, would be better to stay with W7. Microsoft customers said that this problem will be preciselly persistent on 10 % of Windows 10 users, despite this fact, they said that they will fix compatibility issues, but it will take a lot of time, I think one year isn't enough. (AMD Cards are not supported, Intel got only 20 % performance on this platform).