The only Army Sets being Bretonnia and Tomb Kings at launch is a bit so-so with me. I understand GW are usually loathe to drop everything at once, they're clearly awares of how little impulse control a lot of people in this hobby have when it comes to spending and presumably want to spread it out over a longer period.
My issue is that a lot of potential Empire, High Elf, etc players are probably reading that article and going "Hmm... I'll just wait until [My Army] set drops and then get into it." I'm sure in the long-term that won't have much impact on the game, but in the short/medium term it's not great having a lot of people still sat on the fence waiting for their turn. I'm fortunate enough to still have my Dwarfs from before, so it's not much of an issue for me to just grab the two rulebooks and get started, but it's still not great for newer players.
The presence of the rulebook in these boxes also disincentives people from just buying/painting models in the mean time, since none wants to be sat with a second £30 rulebook that you can only flip for like £5 on Ebay, or to have bought a collection and realise if they'd only waited a few months they could've got it all at a substantial discount.
If Horus Heresy was any indication with how they did the Libers, it'll probably be another pair of armies every three months. Although the Liber Imperium and Liber Mechanicum didn't drop with any new models like TOW presumably will be, so maybe it'll end up longer.