On the Star Wars Show recently, Lucasfilm Story Group member Matt Martin appeared on the show to give a preview of the newest ship to the Star Wars galaxy – the INCOM UT-60, which will be better known as the U-Wing:

It’s a troop transport and gunship, so it’s there to bring in rebel troops through heavy fire zones and get out as quickly as possible. The wings move depending on the situation. It’s there to drop off troops and provide air support.
You can see the two different configurations for the ship
Hi-Res imagery below show the The INCOM UT-60 U Wing in more detail.
Matt also points out that the ship has been seen before even if you didn’t realize it, because it appeared in the first bit of Rogue One concept art that was revealed at a Disney investor meeting and Star Wars Celebration Anaheim 2015. In that concept art, we can see a U-wing dropping off troops.
It’s great that we’re getting newer and cooler ships for Rogue One, which is set right before A New Hope, than we did from Star Wars: The Force Awakens. I do appreciate that while they are “new and cool” they look like they fit right in during that time period, unlike anything we saw in the prequels which were set just a couple of decades earlier.