Q.  "Can a FOIA request ask for documents not yet received?"

A.   You can ask, of course, but an agency is required to process only those records in its possession at the time it initiates a search.  Nor is an agency required to adjust or modify its FOIA responses based on what occurs after it provides a response to the requester.  Here is additional guidance from the Department of Justice about "cut-off" dates for agency searches.