I think this task has gotten far more complicated in the last months, because Microsoft is on a strange path with Outlook.
Most people are talking about the Windows desktop version (Win32) when they mention Outlook. Microsoft doesn't anymore; they are completely focussed on the browser client (outlook.com) or their "new Outlook", which is just a wrapped web app with many problems (e.g. security problems: you can't connect it to a company IMAP server without routing all mail content and the login credentials over Microsoft servers).
Outlook (Win32) integrations and connections have mostly been done via APIs like COM/VST on Windows. The former version of the Evernote clipper did (so did the OneNote-importer from the classic Evernote desktop version on Windows, which is gone now), the Outlook-OneNote connection does. But lately a new form of Add-Ins has been introduced to Outlook, that is web based. The current Evernote Add-on in Outlook is using this new format (btw, that's why it doesn't seem to work with non Microsoft mail accounts anymore), OneNote sync still doesn't.
Microsoft already confirmed, that the "new" Outlook (which will not replace the Win32 outlook in MS Office for a long time) will never support the COM/VST Add-ons or other direct communication with other Windows programs. So...if Evernote will sync with Outlook calendars, it's very likely that they will only support Microsoft mail accounts (like with Google) but not your companys Exchange calendar for example.
I can imagine that the Evernote devs are waiting in which direction Microsoft will go with that whole Outlook mess before they even consider to make a move. I'd not expect Outlook support from Evernote for quite a while.
(excuse my English, not my native language)