Thanks @Tamas_Papp for asking.
OK, the post title is a teaser, not a statement about Julia’s maturity 
We use Matlab a lot for prototyping, then Matlab Coder to go faster, then Matlab mcc to avoid licenses, using individual MCR runtime directories for parallel jobs,…
From some translated code I see Julia speed gains of 10x…100x.
The problem is that we will not be able to change horses immediately.
There is the acceptance problem but also complex legacy Matlab code, e.g. design of experiments management (Matlab-on-top).
So the sneaking would be more on the colleague and operational level.
From this the title of my posting.