As a non-Californian and non-US citizen I'm not really bothered what they call the OS. Apart from the fact I think El Cap is probably not the best idea. Just sounds wrong somehow. Maybe because it's a shortening of the name it's supposed to be, I don't know. The thought of OS X Alcatraz made me smile though. With Apple's 'walled garden' what's more walled-in than a prison?
Like others I'm thinking we'll have the name OS X for some time yet. That branding of the "X" is just too easy to overlay on stuff. As for versions, I can see arguments both ways. OS X 10.9 should, logically, for many people be followed by 11. However I get that point release numbers are different than simple numerical progressions.
Personally I'd have no issues, since OS X is the "product", with it being OS X v11.0 - it's not hard to understand. However, I see the logic in keeping the version starting with the 10.x notation since 10 is the OS version referred to by the X in the "product".
As for features? I'm hoping we don't go too far down the flat UI road. I guess we could have more fading of non active elements to differentiate the active window from others but a visual hint as to what's "in front" is always helpful I find.
I'd like to see Find My Friends integrated into Maps. I don't think we need another separate app for this on the Mac since I'm sure it could be a toggle on the map window on such a big screen. And yes, as I write that I realise there's an 11" Air that isn't much bigger than an iPad.
Just my thoughts anyway.