Unless Embraer ramps up its production speed to very fast levels and makes AA (or regional partners like Republic) deals that cannot be refused, AA will probably get some CRJ-900s as well, As a passenger, I much prefer the ERJ175s to the CRJ-900s.
The new AA pilot contract scope exception was written to permit the ERJ-175 and CRJ-900 from a MTOW and seat limit. Anything with more than 76 seats or anything above 86,000 pounds MTOW would have to be flown by mainline crews.