MSPowerUser received word that Microsoft is planning to launch Windows 10 "Creators Update" in April 2017. Thus the version number of this update will be Windows 10 build 1704, which indicates a delay of about one month as previous Insider builds had a version number of 1703. In case you hadn't noticed before, the first two digits refer to the year while the latter two numbers indicate the month of release.
The site's source claims Microsoft is finalizing the feature set of Windows 10 Creators Update:
Microsoft is currently in the process of finalizing things for the Windows 10 Creators Update. The Creators Update is expected to be “feature locked” by mid/late January which means most of the shipping features will be present by that period. That certainly doesn’t mean that the update is “complete” per se, as Microsoft will be working on polishing the new features and fixing bugs before the release.
Furthermore, Microsoft is also working on the next big update, which is expected towards the end of this year. Codenamed "Redstone 3", this build is expected to introduce an improved design language for Windows 10.