Great question — but there's actually no "if" anymore! The A.J. Brown trade to the Patriots already happened on June 1 (from the A.J. Brown page). So the question is: now that Brown is a Patriot, will Diggs still come?
Short answer: It's very unlikely. Per the Stefon Diggs page, Patriots cap constraints make carrying both elite WRs long-term difficult. Albert Breer projects Diggs will land elsewhere (roughly one-year, $10M range) now that Brown is in the fold. Coach Mike Vrabel confirmed the Patriots are "not exploring" a Diggs reunion right now.
But the door isn't completely locked. The same page notes that the longer Diggs sits on the market, the cheaper he gets — so if New England trades a receiver like Kayshon Boutte or an injury hits, a discount return becomes more plausible. Vrabel himself said "I wouldn't say anything is off the table."
For now, prediction markets have Diggs' top landing spots as Washington (33¢/share on Kalshi), Baltimore (30¢), and the LA Rams (10¢) — rather than New England.
On Underdog Fantasy Football, Josh & Hayden noted the A.J. Brown deal finally went through: "It finally happened. AJ Brown is a New England Patriot" — and the corresponding view is that the receiver room is now set with Brown, Romeo Doubs, and others, making a Diggs return a long shot.