There's rumors of an actual time skip for 5G, and you know what? I wouldn't be half surprised if the Kents' early death is indeed retconned, but Pa still died in the Brainiac storyline and even Ma has since passed in the upcoming new present day. They were alive but they'll still be gone in the present. It seems like the type of thing they'd do these days, strange decisions that actually please neither side of the fanbase.