I have a general plan -- order in which I'm going to work on things -- but I don't have ETAs.
Or, I do - but it's of the "should have gotten it done a year ago", not very useful.
As far as calendar goes -- I'm going to add two-way calendar sync for Exchange accounts -- so any calendar events that exist on the server will show on the device, in the system Calendar app -- and there are hundreds of third party apps that work with data in the system calendar.
For other account types -- IMAP and POP3 -- there is no concept of server side calendar / events there.