I see your point, but at the same time I've read both here, at TWoP, and on other forums where people have been critical of the fact that the writers have had these two people who despised each other to the point that they spent centuries trying to figure out how to kill each other - at least Hook did that - suddenly be able to put their differences aside and coexist with each other as if everything was fine and dandy between them. Now they're finally addressing the animosity these two have towards each other, and people are accusing the writers of recycling old story lines. Clearly the Rumple/Hook feud wasn't addressed during Season 3 because the characters spent most of the season apart from one another, and when there was an opportunity for them to interact they were both busy trying to protect people they cared about from the Big Bad Villains Peter Pan and Zelena. They didn't really even have time to be thinking about how much they still hated each other. Apparently, they will be spending more time in close proximity to one another this season, so the writers have decided that this is as good a time as any to revisit their old feud. I would never expect Hook and Rumple to be buddies. The big question here is whether or not the writers manage to write their relationship in an interesting and compelling way, which, yes, is a reason in and of itself to be concerned about what is going to happen.
I'm willing to give it a chance. I think Colin and Bobby play well off of each other, so I think exploring the bad blood between Hook and Rumple could make for a compelling story, not to mention that it will give the actors something more interesting to do than make puppy eyes at some female. As others have mentioned, I'm very glad we'll get to see these characters involved in a storyline that is not focused on their romantic relationships. That is, until a small but vocal group of Pirate Gold shippers start harassing A & E to seize the opportunity to explore a gay relationship between these two characters who have so much tension between them they clearly want each other.