I am sorry for offending you.
I tend to be a bit too blunt at times.

To me, your opening post read a little as if you were seeking validation to keep the items.
I think this is what has caused me to be a bit taken aback.

Legally, I would be very surprised if the company could make you pay return freight.
I also don't think that the police would show up at your door if you did decide to keep the items.
I would in fact, be surprised if the company would even take the time to contact you if they did realise the mistake.
So, no, I don't think any thing will happen if you just keep the items.

Morally and ethically, should you call them?
Some people would shrug and call finders keepers, others would be uncomfortable keeping something they know didn't belong to them.
I am sure you can tell, I am in the latter group

Best of luck in deciding which course to take