Modern goes out of date. You don't call things modern, other people call your things modern.
'Module' is more likely. As in 'app' for 'application'. A 'module' implies something that works with other things so a 'calendar module' could work with a 'contacts module' in a 'modular way'. Apps just do their own thing and are standalone, modules integrate into a whole.
Anyway, this is a speculative story about nothing more than a filing for a name. They should put filings in there for things like 'rocket ship' just to get bloggers talking even more speculative nonsense.
That's not a problem for Microsoft branding. That has a typical shelf life of three to five years.
Also, I think their goal should be to navigate it back to 'Windows' as soon as possible. It's a bit like "the new Coke". Do you think Coca Cola intended that phrase to last forever? (Sorry, couldn't think of another example. Please don't follow up with remarks on how the new coke ended)
I thought so too, and was a bit put off because it sounds like a word a teen in the 60's would use.
But it could also be short for "modifications", as in "XBox mods". (Ostensibly to appeal to tinkerers?)
The best part of a name is, you don't have to explain it -- let people derive whatever meanings they want. You'll often be surprised (and not always pleasantly!) at the unexpected connotations people derive from a name.
So Windows RT becomes Windows Mod and runs only Mods; Win 8.x runs Windows programs and Mods; potentially the Xbox One can run Mods, etc.