All of Gibbons, Noesen & Coleman should be retained, that's a quality group of fourth liners that have the capability to move up the lineup in a pinch as well as contribute on special teams.
I can't imagine it would cost much more than $4 million to get those three signed; around $1.5-1.75 million for Gibbons and $1-1.25 for each of Coleman & Noesen (RFAs). 2 or 3 years in term for all of them. Obviously we have some more kids that might be competing for spots next year (McLeod & Anderson particularly) so it wouldn't surprise me if Boyle is deemed expendable, similar to Lovejoy on defence; thankfully neither should be too difficult to trade with a single year remaining on their contracts.
I think we'll look to retain at least one (likely just one) of our trade deadline acquisitions, I think both have fit in nicely so far but i'd prefer keeping Maroon due to his hard to find combination of size & skill. However I get the impression he'll be the more expensive of the two, couple that with the fact we gave up considerably less to get him and i'd surmise he's the more likely to leave in free agency. Grabner is already established in the area after his stints with NYI & NYR so I could definitely see him having a preference to stay, he's also extremely fast, plays the PK and most importantly knows how to put the puck in the net, things we both need and value heavily. I could see him being a logical fit on the third line with Zajac for the next couple of years until the kids displace them, i'd have no issue with a 2 year $3 million AAV contract for him.
One more thing to consider with Maroon, he's a 29-year old UFA whose value is at an all time high, he's also never had a 'big' payday up until now. He will quite rightly be looking to get paid and for a guy with his skill-set and recent production I could easily see him getting a 4-5 year deal at $4 million+ a year. I don't think we'll be serious players to retain his services for that fact alone, he'd be the very definition of a luxury player given that we already have Hall, Johansson & Wood on that side. He was a shrewd addition for our playoff push given Johansson's concussion troubles and the relatively low-cost we paid to get him, but I doubt management sees a need for him beyond this year.