I'm cynical. I think it works like this:
Announce sets with discount over normal rrp that tie in with new rules etc.
People get excited at the newness and prospect of a decent discount.
Discounts put a positive light on GW's pricing for a change.
GW waits a while for optimum profit and discontinues the sets
Many people are still interested in starting the new project they had planned but now can no longer buy at the same discount so some end up paying the normal price.
The same thing seems to have happened several times before. It's a fact of business that sales are highest after a new release, so GW is doing the sensible (from a sales perspective) thing and generating some hype, some extra volume of sales, and then dropping the discount before the natural decline in sales means they start seeing a net reduction in the amount of money coming in for those products. It's also a great way to hype up models that are not new at all and shift old stock by repacking.
The same thing happened to me with Kill Team - there were a few sets that I wanted because I liked the idea of some terrain on the cheap and something different models to make and paint. By the time my hobby priorities shifted to actually looking to buy Kill Team, the sets I wanted were well out of the picture. In fairness, I probably had over a year to get it together and make a purchase in this particular example, but there has been a lot of other bundles I'm sure disappeared much faster.
By repeating this over time customers start to realise that if there is something they want and it's at a discounted price then they need to buy it straight away or risk losing out, creating a false sense of urgency over a luxury item. We all have hobby plans that we'd like to do if it were a bit cheaper, new armies we'd like to start etc. and a bundle like this is genuinely good in that regard but in my opinion the repeated short lived releases like this are actually bad for the consumer because it pushes you towards making a purchase. GW used to have a fairly rapid release schedule (I'm talking 10-15 years ago) where they would announce new releases a month in advance. The problem they had with this was people would get excited for the new releases but would save their money to see what the following month's releases were going to be. The current strategy seems to be the counter to this; buy now or pay more if you wait. Personally not something I'm a fan of.
I understand that things which don't sell need to be discontinued but limited and short lived releases like are not that and benefit the company more than the consumer. Given that we, the consumers, are the sole reason companies continue to exist, I think it's good to take a step back from time to time and think about whether they way they do business is actually in your best interest. There are plenty of people who will argue about pricing but I don't think enough people talk bout their business practices and how we are sold to.
You should be worried that the apocalypse boxes will disappear forever. They will disappear, though maybe will come back briefly at a later date before they go for good. However what I would encourage everyone to consider is the notion that GW is using the fear of missing out to push customers into making purchases they might not have otherwise have made.