http://tvline.com/2017/01/23/arrested-development-season-5-prequel-new-cast-flashbacks/

Arrested Development's Surprising Season 5 Premise/Format Revealed —
It's Going to Be Part [Spoiler]!
By Michael Ausiello

Get ready to see the Bluth clan like you’ve never seen them before —
and we mean that literally.

Although Netflix declined to confirm/comment, TVLine has learned
exclusively that Arrested Development‘s long-gestating fifth season
will likely have a major prequel element, with potentially half of the
action unfolding in flashbacks featuring much younger versions of all
the principal characters (played by different actors).