I guess we'll just have to disagree on this point. To me, if we see Frieza move past his grudge, then that goes completely against the already perfect conclusion to his villain arc, and if that happens then he's no longer Frieza.
I'm certainly not against seeing villains go through character development, Piccolo, Vegeta, and even Fat Buu have some of my favorite arcs because of it, but the thing is, Frieza did. However Frieza's character development was different than the others, character development does not always mean the character must change and Frieza shows us at the end of Namik and and the start of the Cell saga that his pride, ego, cowardice, and thirst for power define him and he will not give those parts of himself up. Having characters be given the chance to change, and they choose not to is still a perfectly acceptable form of character development.
It's one thing that still stands out about Frieza alone in the series. Even Cell goes through an arc of being cunning in his hunt until he becomes full of himself when he finally has power(very similar to Vegeta during Namik, which is why it's easier to believe that he would be more willing to move past his grudge). That's why I'm still cautious about his role in this arc, it's hard to go any further with him because it can easily not sit right with his already perfect character arc, but if nothing new happens then it will ultimately feel like they shouldn't have bothered.