I won't complain if DL decides to connect all hubs and focus cities to MIA as part of this deal. They're already the
#2 airline in MIA...and United has a significantly smaller share...so by adding some flights in they could, combined with LATAM, probably bump their traffic share to 20%, at the expense of AA.
That said, the only route I care about (AUS-MIA) isn't exactly high-yield already (BE goes for $250 RT) so the more likely scenario I see is LATAM moving frequencies from MIA to ATL based on connecting traffic, leaving just enough service to satisfy O&D needs. Given that AA only serves ~55 US destinations nonstop from MIA, connecting folks over ATL would be a win for everyone except folks in Miami.