As someone experienced in animation and design i can say that Samurai Jack is probably one of the best looking and aesthetically brilliant western animation. When it came out it received both acclaim from audiences and artists. The show was animated by the legendary Genndy Tartakovsky (Sym-Bionic Titan, Dexters Lab, Star Wars Clone Wars) who used an simple yet pure style that has made the show look completely unique. Then suddenly it was gone, left unfinished. Now a decade later we learned that Adult Swim is bringing it back and now we get to see it in action!
The show was notorious for having everyone and everything be a robot so removing arms and legs would be a bit more PG. Now with Adult Swim these limitations have been lifted and man it looks like we are going to see plenty of blood. I feel that the target demographic would be old fans (who are 10 years older at this point) so taking it into a darker more mature story would make sense.
Also animation has become more recognized and respected as a refined art form. The show was ahead of its time which really prevented it from getting too violent or dark but now we have a large audience of adults who grew up watching more mature animated content (especially from Japan). We are starting to dissociate animation as purely "Kids Stuff" and more of an alternative aesthetic to telling a narrative.
If you are not familiar with Samurai Jack please watch this video I found on Youtube of what I can argue to be one of the best fight scenes I have ever seen in a visual media called Jack vs the Shinobi Shadow Warrior (sorry for the low quality).