I read some time ago that GW have quite rigid printing schedules set quite some time in advance, so making changes to accommodate excellent sales is somewhat difficult - and they don't want huge amounts taking up warehouse space just in case it doesn't sell. So they do their best to estimate how many they need to print and that's it for a while - they've had 4 months of pretty strong sales, based on my Facebook (and I don't have that many friends who play Warhammer!). I missed out on the Kill Team Starter Set but now it's unlikely I'll get sucked in even with a new starter set for sale. I guess that's a risk they have to take.
That said, it could all be rubbish
On your last point though, I don't see that the required footprint for KT is any less than Warcry. Minis, book, space to play - all the other stuff just makes it a nicer experience. Don't you also need more than d6s, as well as special cards, for KT?