There are more problems with rotating than it seems at first glance.
1) Cardpool
I come from WotC Standard (which rotates) and the cardpool from Game of Thrones is with 1240 cards smaller than 2 cycles (~1594). And this even counts the plot, house and agenda cards. A smaller cardpool is hampering the playable decks. To make things worse, we have 6 different houses which are very hard to mix, even with cards specially made for that. The cardpool for a certain house is therefore very small and will get smaller with fewer sets.
2) Unneeded cards:
This isn't a problem when you want to play all/most houses with all strategys. And this is also not a problem with a slow changing meta, where you can play for example Maesters for years.
But newcommers and younger players often start playing one house intensivly and with a rotation of sets the metagame would shift very rapidly. They can't afford paying for at least 2 core sets, 6 house packs and all upcomming chapter packs, and playing only one house (which newcommers tent to do) gives them only 2/7 of potentially usable cards. The number decreases with weak cards. This is an actual problem in my meta.
3) The "wow" effect.
In Magic, the best thing to get someone involved in the card game is buying them a prebuild deck and play with him with another prebuild deck. For 10 bucks they get a complete play ready deck with a key card and cards centered around a theme, that are pretty balanced. In GoT you have to buy a Core set for 25 bucks. Don't understand me wrong, the deal is good, but people want to start small. Furthermore the decks in just one core set alone feel a little bit slugish and underpowered in Joust. The frantic fun kicked in as I buyed the second core set and a house expansion, which costed me 70 bucks. This 70 bucks is a more difficult investment in an environment where cards get playable/unplayable at very small time frames.
So first I thought that you need something to make more cards accessable for people that only invest in one house. There are two possibilitys I found: Having something like a dual house card like the banned in the CCG or reducing the amount of houses. The second one sounds radical, but combining the Starks and Baratheon, Targ and Martell, Lannisters and Bolton to have 4 houses. This makes it also easier to split chapter packs into only having 2 houses.
Furthermore I am a fan of having pre build starter decks with a good amount of power and also related to the upcomming cycle(s). This starter decks would contain cards from previous cycles (that weren't in the rotation before) and they would pretty much replace the buying of the core set and the house packs. Such a deck would be published between two cycles for every house and veterans wouldn't have to buy it, because the cards were all printed in the past.