IMO Connie would have gotten over the murder of Carlo very very fast indeed (in fact, she appears to have done just that in GF II), because Carlo beat the living crap out of her, and also betrayed her older brother Sonny, who she idolized, and led to his death.
After her first explosion of anger at Michael at the end of GF I over Carlo's murder, Connie figured out real quick Carlo had been a danger to the whole Corleone Family, including her, and realized she was much better off without him.
She always identified herself as a Corleone more than anything else. IMO she would have had the kids drop the Rizzi name and just go by the Corleone family name. Plus, she ultimately wanted to gain influence and eventually power in the Corleone Family. The way to do that would not be to hang on to the family name of a traitor who had to be rubbed out 30 years ago.
I have to disagree with some of this - I'd like to have seen Connie hold the grudge against Michael forever, however irrational and impractical it was. It just would have identified her as a true Corleone. I never really bought her implicit acceptance of Fredo's murder, given how she begged Michael to forgive him, & the love she clearly felt for him.
I don't mean it's something she would necessarily have taken to extremes, like plotting to kill Michael, but it could have been interesting for her to have brought it up subtly now & then to hurt Michael & remind him of what he'd done, particularly in GFIII, when Michael is somewhat weakened and genuinely attempting to redeem himself.
Had her son been featured, it could also have been something that got out of control, another potentially explosive plotline.
