5.x Series
Released June, 2016
IPython 5.0 now uses promt-toolkit for the command line interface, thus allowing real multi-line editing and syntactic coloration as you type.
When using IPython as a subprocess, like for emacs inferior-shell, IPython can be started with --simple-prompt flag, which will bypass the prompt_toolkit input layer. In this mode completion, prompt color and many other features are disabled.
Backwards incompatible changes
The install_ext magic function which was deprecated since 4.0 have now been deleted. You can still distribute and install extension as packages on PyPI.
Update IPython event triggering to ensure callback registration and unregistration only affects the set of callbacks the next time that event is triggered. See :ghissue:`9447` and :ghpull:`9453`.
This is a change to the existing semantics, wherein one callback registering a second callback when triggered for an event would previously be invoked for that same event.
Integration with pydb has been removed since pydb development has been stopped since 2012, and pydb is not installable from PyPI
IPython 5.0 now uses prompt_toolkit, so any setting that affects readline will have no effect, and has likely been replaced by a configuration option on IPython itself.
the PromptManager class have been removed, and the prompt machinery simplified. See TerminalINteractiveShell.prompts configurable for how to setup your prompts.