GW is not a gaming company, it is a modeling company (why they haven't changed their name to like, Model Workshop or something, I don't know).
That being said, I have to disagree with the above statement that people need a story to 'continue' from a specific time frame. Like the example given, many historical games play pre/post and during a set time frame. Warhammer could do this too.
Stale you say? Bored you say? I say no. What about a campaign, each real year, that focused on a different army/region/realm/etc. of the Warhammer setting. Were people excited by the End Times? Yes! They had new models, a campaign, story driven scenarios, etc. They could do this with so much of the fluff from Warhammer's world it isn't even funny.
The siege of Praag campaign = siege models (would be a hit IMO), new chaos monsters, new middenheim models, etc...
Siege of Uthuan = more elf models, DE models, etc. Story driven scenarios, etc.
I look at Warlordgames and their summer campaign for their WW2 game Bolt Action; Do we know what happened in WW2? Yep. But guess what, the company is engaging it's customers in an interactive way. This (as far as I have read) has boosted sales, encouraged people to swell their armies, paint their armies and get into their FLGS and play some games (well, they haven't started yet, but I'm already gearing up to joining in some games).
To me, it is about the gaming aspect. GW has indicated on many levels that they sell miniatures. I hope people have fun with AoS. They are really good models. I'm just looking for more and hope to keep a bit of the Warhammer community alive with 8th.
Ambrose