As a player, I definitely understand the frustration of having your army get overshadowed by newer releases and the frustration of knowing/thinking that GW won't get around to an update until they are ready to release new models.
But to play the devil's advocate, we need to temper some of our wants and expectations with the knowledge that GW is a business that needs to balance keeping players happy and engaged whilst still making profit margins. Updating old warscrolls and allowing players to continue to use the same old models they have already purchased doesn't make GW more money (I also have very little knowledge on the subject, but I don't believe updating models and making new casts for them is very profitable either).
It may not be healthy for the game overall, but powercreep is what generates the most revenue for them (Getting players to buy whole new factions instead of updating a current army with a unit or two.)
I'm not saying I like it, or even agree with it. Looking at it from their perspective though, I can understand it. I also imagine SCE would be far harder to update, balance, and add to given how many more heroes and units the faction already has in comparison to nearly every other faction.
I understand none of this is news to most of us, but I think that sometimes its easy to forget that in order to pay the people that have to work at giving us what we want, GW has to make a certain amount of money.
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To be more on topic, SCE gets updates nearly every year, so I would expect they get one this year as well, but probably later this year as opposed to the first half since I haven't been able to find any rumors yet.