Sources talking to The Verge have claimed that Microsoft doesn't plan to deliver Sets with the next major Windows 10 update when it arrives later in 2018. We've asked Microsoft for comment on this. However, it's significant that Microsoft didn't attach Sets to a specific release -- it wasn't obligated to ship the feature in a set time frame. This won't be much comfort if you were hoping to use app tabs before 2018 was over. However, it does suggest that Microsoft is more interested in nailing the experience than shipping a feature purely to tick a checkbox.