Think about it for a second. When Barry committed this act of going back in time, (an act which I think was selfish and irresponsible) It created the Flashpoint time line, in which Wally was powerless and eventually murdered by Captain (at that time Citzen) Cold. When he finally "fixed" the timeline it wiped him from existence. Now was his death in Flashpoint that led to his absence in the New 52? Either way Barry is ultimately responsible for the current non existence of his nephew, on of the people who loved him the most. Do you think that Barry will be able to forgive himself if he ever remembers Wally. With these connections made, given his history with Wally, this is something serious to think about.