A decision about the future of Belmont Park is expected to be announced at a news conference Wednesday at the racetrack, according to two people familiar with the situation. The site will either be the new home for the New York Islanders or the New York City FC soccer team. Gov. Andrew M. Cuomo is expected to be on hand, the people said. The anticipated announcement comes on the heels of a public hearing at Elmont High School Dec. 10 in which developers representing the Islanders and NYCFC released some details about their competing proposals. The Islanders want to build an 18,000-seat, year-round arena that would host 150 events annually as well as 435,000-square feet of space for retail, a hotel with 200 to 250 rooms and a 10,000-square foot “innovation center” that would be developed with resident input.