We have exited beta now, as far as I can tell.
However, the site looks identical to most beta sites.
When will we make our own design?
As far as I know SE is looking into implementing new features, which PPCG would also benefit from. It seems that they want to wait with producing a design until those features are worked out, because the design could be affected by them, see e.g. here.
I'd actually prefer it if the site doesn't get a design at all; the vast majority of Stack Exchange designs make the site both ugly, and hard to read at a glance, whereas the beta theme is clear and simple.
Even if the site does get a design, there are changes which are rather more pressing; this post lists a number of potential changes from Stack Exchange's end that could help the site function better, and many of those have higher priority than a design would. Things like a custom Tour page would be highly useful, because the site interface currently gives outright misleading information on how the site works.