Yes they will get eaten.
They have perfected their ambush skills for many millions of years pass down trough DNA. Barbs and danois only came later. Even the fastest fish in the world will still get eaten as long as it fits in their mouth.
I agree to a point but i think it will be a while before they get eaten. And it may not happen at all.
It all depends on how big your tank is and i so are there hiding places.
The biggest threat will be Stress on them that will kill them.
He might get lucky but in a big tank doubtul.
If your intention is to keep them with some cichlids or Gars then it's just a matter of short time.
Poly's are mainly scavangers they go by feel and not sight (mainly)
you don't believe how vicious an ornate can be until its too late, belive me they can and will eat fish waaayyyy bigger than you can imagine, i learn that the hard way
Would be interesting to see how long it takes before they get eaten if you keep it well fed. I've found my ornates predator instincts only really kick in when he's hungry, chasing pieces of shrimp is much easier than chasing barbs and danios, so you might get away with it for some time.