[This is not an official nLab position, just my take]
Sadly, the current system of academia actively disincentivises such novel experiments. It's hard enough to set up a new journal to effectively replace a journal run by some for-profit shareholder-pleasing company, although it has been and can still be done, with a lot of goodwill and determination by sub-communities of the mathematics world. Setting up a wiki-journal is even less respected.
The Steering Committee of the nLab (which doesn't run it, officially) hasn't done a post-mortem, or tried to dig into why the journal didn't take off. But it's clear from the relative lack of 'official' recognition Urs had gotten, for instance¹, for having the largest hand in creating a piece of impressive scholarship, that some kind of journal run along the same lines and asking others to risk their careers is not going to be a roaring success.
Recall that 2012 was 'peak Elsevier', people were quite fired up and willing to think about new things, even if briefly. But look at a really serious attempt to change publishing by Fields Medallists at that time: Forum of Mathematics: Pi, which published three (3) articles last year, compared to the 33 in the Annals (the intended competition), over 6 issues. (to compare: FoM:Sigma published 24 last year, fairly respectable given the selective nature)
¹ I mean: he accepted an affiliation in the Middle East, in addition to his position in Prague, not exactly Scholze-level career recognition :-)