It's pretty much confirmed the games won't be released in west. Why? DQ isn't as big here as in Japan, but still have a nice cult following and the last entries sold well around here at the 500k mark for USA and a little more in Europe. Because it's and MMO? 

MMOs aren't as popular in the west as they used to.

They have been replaced with Free To Play mobile games... 

It's an MMO, that's why

Dragon Quest sells millions in Japan.
Dragon Quest sells a few hundred thousand everywhere else, cumulatively per release.

Dragon Quest X is an MMO that relies on a large and constant subscriber base.
Dragon Quest has bred an audience of largely single player focused JRPG lovers.

The reality of it is that Dragon Quest X is just not a fit for anywhere but Japan, and it was even a questionable fit for Japan, really. Between the heavy MMO competition in the West, the general niche appeal of Dragon Quest outside of Japan, and the cost of localization and server upkeep, bringing Dragon Quest X west would be an incredible waste of time, effort, and money.

Yeah, its because the series isn't big in the west and it would just cannibalise on their FFXIV fanbase.

Unlike others say, its not because MMO's aren't popular in the west, because WoW is still a beast and theres many players spread between other MMO's.

It just doesn't make business sense.

It's too much risk, especially for a MMO, let alone a Dragon Quest game. But I feel if it was marketed right, DQX would perform better in the US than Japan. From what I have played, it's a very interesting and different MMO RPG. I honestly couldn't care less about DQX though. It just isn't for me.

Pretty much sums up what I was going to say.

It's an MMO, which means they would need to maintain servers for the game after release, which probably isn't viable given how many people they expect to play it. It's annoying for people who want it, but they're also a business, not a charity. *shrug*

Personally, I'm excited that VII and VIII remakes are making their way over here, so I'm not really bothered about the lack of X in the west.

Because it didn't do that well in Japan and MMOs are a really big gamble to localize