The thing that makes me believe Wally would have reappeared is in the manner in which he disappeared. I mean he wasn't straight away vaporized by the energy. He became more and more translucent and then simply faded away. Why would he have become translucent before dying? And the way his death was phrased that he had 'ceased' make me think that he vanished to a different dimension and a had ceased to exist in this world.
Anyways, as a big Wally fan, what pains me is the lack of reaction to his death. The scene with Artemis and Wally's parents was moving. But barring Artemis, Bart, Nightwing, and Barry and Kaldur to an extent, we didn't get to see the emotional reaction from the rest of his team mates. Not even from Megan and Connor who were his original team mates. It seems like his death was just as significant as Tula's within the context of this show which shouldn't be the case since Wally is an original founding member of the team.
I agree with the first part.
And I can see your point, though I believe the reason for the lack of emotinal reaction was the short time they had to end the last episode. There were too many things to happen, so they had to give more importance to the facts, the story, not isolated characters.
As there was a third season planned, I'm sure they'd explore Wally's death with more details and with more characters. Even because there'd be the possibility of having him back.