Cash shops do not stifle development. They aid development. Sure there will always be people dedicated to producing content for the cash shop, but the money from that ostensibly goes towards paying for the development of other content.
New content is expensive, moreso than you'd believe.
There's this one huge fallacy with development TEAMS players seem to be under. They seem to think that if a company is doing one thing, then they aren't doing another. There's an assumption that the people developing items for the cash shop are people that could be working on something else.
Well...that's only marginally true. Testers and marketers are really the only ones that overlap. The people running the store most likely have that as their sole job in the company. People designing things for the store either have that as their sole job, or are working on variants of things already in the game.
Let's take a look at what actually IS in the store:
Eternal Bond: Probably the more controversial since the bells and whistles versions cost money. They've been working on this for a long time, and the basic concept itself is absolutely free. Paying for it just gets you extra doodads, much like a Collector's Edition of a game...of which this game has had TWO, by the way. The way it's implemented is exactly what i'm talking about. Everything in the system is available for free within the game with the exception of aesthetic gear, which are all variants on things that already exist.
Sleipnir Mount: It's a mount that costs money. It's also the top seller in the cash shop. Yeah. Offers no advantages other than looking cool.
Minions: They're freakin MINIONS. They've had "premium" minions for the longest time (remember they've been pre-order bonuses and CE bonuses in the past) and whoever's designing these things probably wishes they got to design more.
Dyes: A variant of something already in the game, again. It's pretty much tradition at this point for cash shops to sell special dyes. There shouldn't have been any surprise at these.
Seasonal Outfits: Admittedly this one was a little disappointing to me, as there were a couple holidays i missed that have things i want and now i gotta pay for em...but oh well. They were already in the game for free, and everyone had a chance to get them for free. Now, they cost money. It's actually a good business decision, even if people are unhappy. Makes me appreciate the items i got, though.

None of these would take exceptionally more time to create than anything else. Sure there will be some larger scale marketing things coming out (Triple Triad WILL be monetized. It's a card game. That's what card games are for.) but most of this just seems to be things for the art and animation teams to occupy themselves with between working on the massive, interesting updates we've been getting.