Nothing prevents implementation of any of those features, other than the fact that browser platforms don't allow some basic features to work.
Copy paste? No, not without Flash. Calendar notifications that work when the browser is closed? Custom fonts? Vertical text? Software that doesn't rot? Accurate page layouts?
If these new functionalities were so good and browser integrations were so powerful, then phones wouldn't need app stores, GMail/Google Docs wouldn't have a mobile application, etc. I'm more than ready to bet that in a decade, there will still be a desktop version of Office.
What? Of course copy paste works, even with formatting. Or, at least it does on my machine. Spreadsheets are trickier, but there are ways to override the context menu to make it do-able. I assume Google docs can already do it. Haven't tried it specifically, but I don't remember not being able to...so pretty sure I have copied and pasted within a docs spreadsheet.
"Calendar notifications that work when the browser is closed?"
Why would your browser be closed? This is the future we're talking about. Your desktop and everything else will be in your browser. That's like complaining that notifications don't work when your computer is unplugged.
"Custom fonts? Vertical text?"
Already possible and covered by standards. Are you using IE10, or something?
"Software that doesn't rot?"
Hahahah. Funny. How's Visual Basic written ten years ago holding up on Win 10? Sure, it probably runs, but nobody wants to use it. Platforms evolve. Standards compliant HTML and JavaScript written ten years ago is still functional. What do you believe is uniquely prone to "rot" about the web platform?
All of the app stores have hundreds of apps built on web technologies. Google has a mobile version, but does not have a desktop version. In fact, GMail (and moreso, Inbox) are much better evidence for the case I'm making (that the web will devour almost every class of software in a decade) than the case you're making (that office software like Word and Excel are uniquely immune to being devoured). Inbox is a better mail client than Outlook. And Docs will become a better doc suite than Office...or somebody else will build one that is (might even be Microsoft that builds it...if they're smart, it will be).
Copy paste? No, not without Flash. Calendar notifications that work when the browser is closed? Custom fonts? Vertical text? Software that doesn't rot? Accurate page layouts?
If these new functionalities were so good and browser integrations were so powerful, then phones wouldn't need app stores, GMail/Google Docs wouldn't have a mobile application, etc. I'm more than ready to bet that in a decade, there will still be a desktop version of Office.