Here's what I found on Wikipedia about the map "Longshore." This map is expected to be released with Assembly, Orbital, Sandbox, Citadel, and Heretic in the Mythic Map Pack. "...in early 2009. “Winter,” as they say." -Lukems in the 10/10/08 weekly update. This map contains a hidden skull. Locating the skull earns the player the 'Longshore Skull' achievement. [1] This map's only confirmed vehicle is the Ghost. This fact supports the theory of a Relic remake or at least a Relic inspired map because the Ghost played an important role on the map. Longshore suggests longshore drift, a geographical process for beach deposition. This hints that Longshore has beaches, as Death Island and Relic do. There is also a possibility its a remake of Headlong from Halo 2. Headlong also had a bay, and it is a similar Snipers type map as Death Island and Relic. Splattering thrice with the Ghost on Longshore will gain you the Achievement Ghost Patrol
I loved relic, but I wasn't a big fan of headlong because it felt empty. It's probably something new. Something like a resort or an island.
It'll be something new, but a spiritual successor of Relic. Didn't the ring that Relic was on go off?
I'm really hoping it's headlong. Really though, based on the name, there really is no way to tell. They changed lockout from a frozen wasteland to an oil rig. (Personally I don't like some of the changes they made though, rendering some jumps unable to be done.) So, they might change the small 'bay' area in headlong into a fully-fledged beach. There's no set answer, you know? Well, the ring that relic was on Delta Halo (Installation 05), and it wasn't blown up at the end of Halo 2, thanks to Miranda Keyes, remember? Installation 04 was blown up twice though, in Halo: CE and Halo 3.