Is there a shortcut to get to the bottom of a long email on iPad or iPhone?
iOS does not provide a shortcut for skipping directly to the bottom of documents, but there is a reasonable alternative, if you're not already aware of it: scrolling views in iOS respond to swipe frequency, scrolling more quickly the more quickly and frequently you swipe the screen.

While swiping a long document, email, or webpage, try several long, quick swipes in rapid succession: you should notice the scrolling speed accelerate accordingly. This isn't nearly as elegant as a tap shortcut, but does let you quickly skip to the bottom of a long view.