Google is still planning to include on-the-fly, but it won't be arriving in the coming days as previously revealed.
A Google spokesperson told CNET that engineers decided to hold back the feature because of software problems discovered in the final testing phase.
Apparently, "multi-language support is complicated stuff and they found some bugs during their final testing phase that they wanted to fix before making the feature generally available," the spokesperson said. The feature is now expected to ship later this summer.
at the same time as Google I/O last week, but not as part of the I/O announcements, the feature would allow a multilingual Google Now user to select up to seven languages to support in addition to the default language on their device. You could then choose to use any of the languages to ask Google Search questions and set reminders in Google Now.