Although Pietro died a devastating death in Avengers: Age of Ultron, it stands to reason that there's hope he'll make a comeback in WandaVision. As we saw in the third episode, his death still weighs on her. Actor Aaron Taylor-Johnson has said before that he wouldn't mind returning to the MCU, "if there's an interesting story, and an interesting character journey in that world." Safe to say, any return in this series would be interesting! So the question is, would Pietro appear as a memory or as back from the dead like Vision?
It would be fruitful to flesh out Wanda's backstory if fans get to see more of her past with Pietro and their family in Sokovia. But admittedly, it would also be amazing if her powers brought her brother back from the dead like she does in the comics.