From the bug report it looks like they will allow users to choose safe software sources. Presumably this means you could add userscripts to this list and regain the old functionality. It's just not done yet.
This change was made to protect users. Off-store extensions have
become a popular attack vector for compromising users of larger
sites (e.g. Facebook). Since the trend is only getting worse,
we're putting the power back in the user's hands by allowing them
to control where extensions are installed from. By default, the
Chrome Webstore is the only source, but users and administrators
will be able to add other safe sources as they see fit.
