When I visited earlier this year, I had the chance to talk to a couple of the people involved. I got told that they were hoping for a (late) summer opening, so August/September, and also blamed Brexit and Covid.
It's a shame that they are still unable to get around those issues, but it's hard to blame them. The project is (obviously) more ambitious than everyone thought it would be. And with the amount of money sunk into it, they have every interest to open it as soon as they can, to start to recoup the investment.
A good news at the end:
From what I was told, not only every single effect will be updated/renewed, but they would also add additional effects as well.
Thanks to the Liseberg and Europa-Park annual pass, I have 2 free visits to BPB 2022, and I would like to use at least one of them to get back onto Valhalla. And as many flights go from Manchester to Katowice, you can bet that I'll find a reason to make the departure to England again.