DLC: Quarian Ark

The story of the quarian ark is told in the novel "Mass Effect Andromeda: Annihilation" by Catherynne M. Valente.

The game will almost certainly not receive any new DLC.

But why Legendary edition its same Mass Effect 1,2,3 as old nothing change but Andromeda has a potential with some improvments why EA abandon this concept and never create quarian dlc or andromeda 2.

Mass Effect Andromeda probably didn't sell well enough to justify the cost of a making new DLC. The studio that made the game isn't even part of BioWare anymore. They merged with Motive and are now making the Dead Space remake.

Mike Gamble, who is in charge of the next Mass Effect, said the game will connect to both the Shepard trilogy and Andromeda, so we may get closure after all.

But in the trailer for the new Mass Effect when camera fly through rubble it seem like destroyed Nexus Station then how EA planned connect both games without proper end of Andromeda.

@Aerestes 

It was a destroyed Mass Relay.

All the rubble was in the Milky way. 

Yes, that was definitely a destroyed mass relay. The establishing shot of the trailer shows two galaxies, with the distant one being Andromeda. This was a deliberate choice because the lead producer said that Andromeda will not be forgotten.

Whether Andromeda will get a proper conclusion is unknown. I hope it does, but it will be tricky story-wise.