I don't know if that's me over speculating or if it's Monolith Soft teasing us, but go and take a look at the official page of Xenoblade X (xenoblade.jp).
The page's layout has changed, but we don't care about it (cause no additional music for now...). What brings me the possibility of seeing a Xenoblade X demo is that Japanese phrase over the "Information" panel.
In case where you don't get what I mean, I'm talking about this:
"2015年4月29日 発売 パッケージ版/ダウンロード版"
Don't Google Translate it, it makes no sense. But using my very limited Japanese knowledge, we'll analyse the phrase.
"2015年4月29日" -> April 29th, 2015
"発売 パッケージ版/ダウンロード版" -> roughly translates to "published downloadable package/downloadable version
Which means: "On April 29th (2015), a downloadable package/version will be available"
Of course, I don't know if this "downloadable" thing will be Japan-only or it'll be a worldwide thing, but I think a future Nintendo Direct or some info Takahashi might give us will confirm it.
So, maybe we'll get that sweet demo they showed us at the E3 2014 !