There has been continuous upgauging of aircraft in Charlotte from the old US days. Went from a mix of mainline 319/320/321 to more 321s as 321s got delivered on both the US and AA side.
Charlotte is gate limited and doesn't have that many wide body gates. There is also a long concourse of RJ gates. We'll likely continue seeing cr2s got to cr7s and cr9s. Going from a 50 seater to a 76 seater is a big bump on a percentage basis and doesn't take up more gate room. PSA has gotten a lot of addition Cr7s and Cr9s, and retired some Cr2s.
My guess is less exciting but bigger RJs.