God's becoming "all in all" requires neither God's absolute sovereignty over all things nor the absorption of God into creation. In the New Testament, as in trinitarian theology, it is better understood as a way to speak of a personal relation between Creator and creation and between the Father and the Son.
Word & World
Fredrickson, David E. “God, Christ, and All Things in 1 Corinthians 15:28.” Word & World 18, no. 3 (1998): 254–63. https://luthersem.idm.oclc.org/login?url=http://search.ebscohost.com/login.aspx?direct=true&db=rfh&AN=ATLA0001003088&site=ehost-live&scope=site.
Fredrickson, David E., "God, Christ, and All Things in 1 Corinthians 15:28" (1998). Faculty Publications. 72.