That's one plausible interpretation. However, I'd like to offer a different--and perhaps simpler--explanation.
Perhaps Blizzard is removing the Upgrade Vendor NPC in 5.2 so that they can bring him back in 5.3.
See, the thing is that--given Blizzard's current goals for patches--5.3 is probably not going to include a raid. I imagine that it will be a patch very much like 5.1 was. A new reputation, a new storyline, lots of random side-events. Those sort of activities only ever reward sidegrades. They won't offer true upgrades a tier higher than the current raids.
Of course, character progression is still important. I think Blizzard still believes that a patch without any way to improve your character will not be popular with their playerbase. That position could very well be correct.
Bringing back the Upgrade Vendor in 5.3 allows people to continue improving their gear at that point. You continue raiding to fill out missing pieces and earn Valor to improve your current gear.
This is a much more likely plan for Blizzard. Upgrading gear probably required a significant amount of tech to implement, and it is very unlikely that they did not foresee any mechanical issues (with scaling, etc.) that would result.
So I think the plan looks more like:
- In 5.2, players upgrade their gear by doing the new Thunder King raid and getting new items.
- In 5.3, players upgrade their gear by spending Valor on the gear they earned in the previous tier. All the non-Royalty guilds will also still be progressing through the Thunder King raid, and earning new gear that way. And of course, filling things out with sidegrades from the new non-raid content.
That's more plausible than Blizzard suddenly deciding right now that the entire concept of upgrading gear was a mistake.
Update: Looks like I was right! Post from Bashiok:
Update: Looks like I was right! Post from Bashiok:
Even Ethereals need a vacation, and the item upgraders (Voidbinders), are no exception. They’re saying they need to go home to take care of business arrangements, but … I’m not convinced. I think they’re just homesick for their ‘space mummy’ families.
Ok ok, fourth wall broken, we’re actually just temporarily removing them from the game for 5.2 due to the new raid tier. The idea with the item upgrade system is that it’s a way to spend currency on upgrading items when buying new items isn’t the clear path. Either you’ve bought everything, or at least most of them, and then spend currency to get that extra *oomph*. With a new raid tier coming, we don’t want to create a trap where people are wondering what’s more lucrative: spend currency on new items, or on the new gear appearing on vendors? (Hint: It’s the new gear on vendors.) To help ensure we’re not indirectly encouraging anyone to spend their currency somewhere they probably shouldn’t, the item upgraders will be taking a break.
Right now we’re planning for them to return in 5.3, which will not have a raid tier, and offer upgrades again as people will have likely have some currency to burn. We’re not sure yet if we’ll continue this cycle of having them take a break for raid patches and then come back in non-raid patches, but we’ll continue evaluating as we go, absorb feedback, and let you know how these plans evolve.