From the press I’ve read for this series, it looks to me like Kara and Helena are going to still be together in this weekly. The fact that it’s been confirmed Marguerite Bennett is writing their story arc seems to suggest that they’ll be by fighting together in their respective story arc. She’s also stated on her personal Twitter that she enjoys writing them both and writes them like sisters looking after each other.
Also from the artwork I’ve seen for this series, it looks like Thomas Wayne will still be paired off with Jimmy Olsen, and Val-Zod could very well be paired off with Red Tornado.
That being said, I too dislike how both Huntress and Power Girl were demoted as the legitimate successors to Batman and Superman in the New 52. Val-Zod I’m honestly not bothered by, but DC did NOT need to remove Kara from her own narrative to service him.
Thomas Wayne, on the other hand, there is simply no excuse for him existing on this world, period. Batman does not need a male Wayne to succeed him, a fact that was easily proven with the pre-Crisis Helena Wayne who was a fan favourite. If Huntress could prove in the 1970s that you don’t need a new Batman for the Earth-2 franchise to be successful, there is absolutely no reason that same idea could not have worked in the year 2014.
But the problem, as you say, does go back to sexism. It’s part of the larger problem with the current leadership and why many of DC’s books are not as successful as they could be. The current leadership has made it clear that they write for men first, everyone else second. It shows in which characters and narratives they prioritise and promote (especially Batman) and which ones get tossed into the sidelines, including characters (like Lois Lane) that shouldn’t be there.
With such an abysmal track record, Dan DiDio—if he’s smart—should not be surprised by ‘excitement [for the New 52] dying down.’ If the only way he knows how to get people to care is by sacrificing quality for the sake of selling shock value, or course people are going to lose interest. That should surprise no one. It’s symptomatic of bad business practise.