Microsoft was expected to roll out Windows 10 Spring Creators Update Official Version (RTM) on April 10th but postponed. On April 11th, Microsoft had roll out a cumulative update of Windows 10 RS4 Preview 17133.73, which in fact had confirmed that Build 1733 is a Windows 10 Spring Creators Update Version (RTM). But it will take time before it is rolled out by Microsoft.
Microsoft discovered a blocking bug last weekend, although it was very rare but enough to affect the release and rollout of Windows 10 Spring Creator Update Version until the problem is completely resolved. Microsoft owns an intern testing system which requring every rollout and release of major system versions must passing it. This bug was found in Windows 10 fast, slow, and release previews version.
It is worth noticing that the Windows 10 Build 17133 version will still be RTM, and Microsoft will fix the vulnerability through a cumulative update. By tradition, Microsoft will announce the official name of Windows 10 Version 1803 in advance, but this time Microsoft has remained silence. Perhaps in the near future, Microsoft will announce the official name of Win10 1803 version and the exact date of rollout.