Most likely, the allies who sprung him from the far reaches of space have been a part of a power play he has had cooking for years. The general consensus from those working on the show is that Ahsoka will have multiple seasons. The story/cliffhanger will likely pick up in the second season of the series or 4th Season of the Mandalorian. Looking at the grand scheme of things and the information, this particular attack/war is what will really allow the first order to rise. As for the fate of our heroes, not everyone will make it back. As per sources, Ezra makes it home but one among Sabine or Ahsoka does not, most likely Ahsoka.
Ahsoka Episode 8 – Thrawn Defeats Ahsoka & returns to the Empire – Scene (HD)