I am pretty sure Locke's father will show up on the island at some point.

My only evidence is that his last name is Cooper, which I think is a reference to D.B. Cooper.
http://en.wikipedia.org/wiki/Db_cooper

D.B. Cooper was a hijacker who was last seen jumping out of a plane with a bag of ill-gotten money. Locke's dad was last seen getting on a plane (shall we assume Oceanic Air?) with a bag of ill-gotten money. It is a common occurrence on the island for people and things to fall out of the sky, and we all know Locke has unresolved issues with his dad.

That said, other people have pointed out that Locke's dad shares his name "Anthony Cooper" with the philosopher "Lord Anthony Ashley-Cooper" as other losties share names with famous philosophers. However, I've heard of Locke and Rousseau. Who's ever heard of "Lord Anthony Ashley-Cooper"?

Plus it seems likely Locke's father is the con man Sawyer is looking for. When he shows up on the island Sawyer will get his chance to kill him and Locke will need to confront an ambivalence about whether to protect him or not.

Also notice D.B. Cooper's ransom was $200,000, the same as Locke's cut in Lockedown. And now I'm reaching...