The iPhone belongs to the little girl’s mother but one assumes she’ll have her own (or her mom won’t). They’re watching YouTube videos (I believe I hear the lilting strains of “Friday”).
The iPhone will be a transparent part of their lives (rather than the magical device it is for us). As adults, they’ll laugh at the quaint old iPhones of their youth (think rotary dials and party lines). How they will communicate in that oh-so-close future, I cannot imagine.