As of right now, the two commemorative coin programs for 2014 (Civil Rights,
Baseball Hall of Fame) and 2015 (Marshall's Service, March of Dimes) are set. Only one of the two available slots has so far been filled for 2016, however. It's the Mark Twain program which calls for a gold half-eagle and a silver dollar.
Of the various commemorative coin bills that have been introduced in the current Congress, only two call for a 2016-dated coin: the National Park Service 100th Anniversary Commemorative Coin Act and the Pro Football Hall of Fame Commemorative Coin Act. Of the two, the National Parks Service bill appears to be "in the lead."
Each of the coins has had a bill introduced in each chamber of Congress, but only the Parks Service bills have listed co-sponsors that total roughly 70% of the members of the House or Senate, as appropriate. The House bill has 306 co-sponsors (out of 438 House seats) and the Senate bill has 73 co-sponsors (out of 100). In contrast, the Senate version of the Football Hall of Fame coin bill has just 24 co-sponsors and the House version has just 34.
Maybe sensing the uphill battle it faced with the bill it introduced early in 2013, the sponsors of the Football coin proposal introduced a new bill in December which pushes the year of issue for the coin to 2017. To that I say "Good Luck!" There are already several coins proposed for 2017 and there is still time to add more.
Returning to the National Parks Service coin, I think the Senate bill might be the more likely to emerge from its designated Committee and ultimately gain approval due to the fact that both the Chairman and Ranking Member of the Senate Committee on Banking, Housing and Urban Affairs are each included among the bill's co-sponsors. In contrast, none of the leadership for the House Committee on Financial Services is a co-sponsor.
Each version of the Park Services bill was referred to its designated Committee during the first half of 2013, with neither seeing any movement since. Normally, I would read this as a lack of support for the bills but the number of co-sponsors argues otherwise. Only time will tell, however, as it's always possible that a new coin could be proposed that captures the attention of Congress and sails to approval. Personally, I hope the National Park Services coin gets approved for 2016.
As I mentioned above, there is already competition for the one 2017 slot remaining. In addition to the latest Pro Football Hall of Fame bill, there are also pending bills for the Boys Town Centennial, the US Coast Guard, and the National Purple Heart Hall of Honor.