With the recent appearance of the ravager and fiery horse store mounts (well, presumably), that brings the total number of mounts available for purchase to 9, not including their various other promotions (Digital Deluxe editions, SoR, Recruit-a-Friend, etc). This isn't really that big of deal, but it seems like they've started adding mounts A LOT more frequently lately.
Besides mounts and pets, they started adding more and more additional things to the shop. The transmog helms (which were and are way overpriced), the experience elixir and charm bag (for Asia only), and the Boost to 90. Plus, the store has become far more prominent and in-your-face - look at the addition of the in-game shop as well as the button allowing you to buy things on the character select screen.
I don't think of the items on the store have crossed the line into pay-to-win territory, but I feel like they could end up there. Even if every item is entirely cosmetic, it feels like they're starting to spend far more time and resources on store items compared to things available in-game. Compare the Iron Skyreaver and the Fey Dragon to the other mounts added in 5.4. The Sky Golem holds up, but the Galakras mount, the Kor'kron Wolf, and the Juggernaut all seem lackluster by comparison.
This makes me wonder, why is Blizzard stepping up their game with regards to the store? A few months back, they were even establishing a "Microtransaction Strategy" unit, hiring some new people for it. Obviously, with the introduction of Hearthstone and Heroes of the Storm, Blizzard is entering the free-to-play market. Do you think they could ever push WoW in that direction? Blizzard already makes a big chunk from the store alone (213 million in 2013 - League of Legends made 624 million, meanings WoW's cash shop makes more than a third of League's total revenue).
Tons of games have seen success after making the switch, and while WoW still dominates the sub market, it's in a decline. Once it slips a bit more, wouldn't it seem like a good idea to go free-to-play? It has the potential to reinvigorate the game. I'm sure there's tons of potentially or formerly interested players who just can't justify the sub fee when compared to games like League of Legends, but would love to play, and quite probably pay for things like cosmetic microtransactions.