Early childhood special ed teacher here.
It's too early to tell if your child should be held back from K. As PPs said, a lot of good stuff happens this year that gets most kids ready for K.
If he has a sibling that is delayed, that may be even more reason to send him to Kindergarten on time, to make sure he is doing social-emotional learning among typical peers. That said, there is always the possibility that he may benefit from another year of ECE - mention your concerns to his current teacher and touch base with the teacher throughout the year so you're up to speed.
One more thing - it's pretty hard to hold a kid back in DCPS without an IEP. (I'm not familiar with how charters do things). So unless the child is truly, truly behind, DCPS will push for you to send him to K.