The legacy software being the reason not to call it windows 9 doesn't sound plausible to me...

Either there were some lazy coders back in the day that looked in a strange place for the version number or it's not true.

The reported version strings are in line with an entirely different scheme; 4.xx for 9x to me, 5.xx for 2000 & XP, 6.xx for vista & 7, haven't checked the ones for 8/8.1 as yet as I haven't coded against those platforms as yet.

They called it Win10 because 10 is better than 9 and further away from 8. Just marketing. The real version number will be hidden in the OS somewhere (sorry see ^ has just mentioned that)

 

They'd have called it Windows X but the 'nix guys grabbed that years ago. I thought they might have gone a bit Spinal Tap and jumped to 11.

 

MS are getting back on track, Most businesses will hand onto 7 now until 10 is ready.

 

The core of Win8 / Server 2012 is pretty solid, 10 will be more of a reskinning job; probably more an evolution of 8 than anything dramatic.