The spin-offs are irrelevant here. From 1 to 2 to 3, each one made their own changes and improvements.
The main sellling point of the games is the story and gamplay. So obviously they can't change the gameplay since its what made it so succesful. So what they must change with each game is the story, keep it going. 

Ascension is a prequel and it introduces some sort of time travel ability for Kratos which could explain what happens in God of war 4.

I would love for God of War to continue without Kratos or his story or that mythology.

Norse religion would be awesome for God of War. You could rip apart Thor and Odin and Loki and all the other Marvel characters (jk). Seriously though Norse mythology or Egyptian would be an awesome setting with a new protagonist. The gameplay can be minorly tweaked but keep the name because it'll still be qtes, giant bosses, killing gods, and awesome hack and slash combat.

pretty silly article. If a game can bring joy or excitement to enough people to make a profit then no franchise needs to stop

Riderz
DmC is in huge decline since the first one, is not the same, i think GoW3 might be the peak in terms of sales, Ascension is going to sell nowhere near 3, and GoW 4 is so far away that the series popularity is going to be hard to maintain

The IP should definitely continue, but I wouldn't mind seeing a new main character and setting.

Or perhaps have Kratos wage war against Asgard. I would pay money to see Kratos kill Thor. Seriously.

Or perhaps totally whore him out like Mario. Metal God of War, Darkness God of War, maybe even God of War brothers.

OK, the last was a joke, but Kratos taking on Asgard would be awesome.

Egyptian setting would be awesome! Thats what im rooting for!

God of War is easily one of my favorite franchises of all time.

But in a way I agree. Simply because God of War 3 didnt leave anything open. -spoilers - I mean Kratos freaking kills EVERYONE.

The gameplay and graphics of the franchise are absolutly top notch but really from a story perspective theres no where left to go.

Fuck! this article is here too? I just read this article in N4G. Why would they stop if the games are amazing and sell like crazy? (even though VGChartz undertracks them).

Stupid article is stupid.

Well, considering the ending, and how Athena behaves, I would say that it has some ways to continue.    If the greek Gods were the top of top, how the hell is it is possible for Athena to be on a higher plain of existence?  I will go crazy and say that Uranus (father of the titans) is alive and wants to take what is "rightfully" his back, and so he was using Athena as his agent.   If you played Ghost of Sparta, you know that Athena on purpose select Deimos instead of Kratos, and even "protect" him against Ares; I bet she knew that the oracle profecy was talking about Kratos and not about Deimos.   Also after GoS Deimos goes to Hades, because there is no Tanatos anymore, and he could have escaped out of there.  If Kratos can do it 3 times, why wouldnt Deimos be able to? Also in GOW3 you can read some notes which look like to be written by Deimos (who can not seem to remember that Kratos went to save him???). 

There are many unanswered things that can be the foundations of GOW4.  Also the Furies according to Greek mythology appear from the blood of the severed genitals of Uranus (Chronos castrated him) RE LOL XD.  So if they are talking about things related to Uranus in Ascension; I think it is in order to provide more backstory for GOW4.

While I dont think GOW is an enjoyable game to play, it is a blast to watch. Id love to see the teams that put together the GOW games work on something different. No good reason to stop the series though.