Sabo inherited both Ace' power and will. Will doesn't mean that he holds a grudge against Akainu, but rather that he may act in Ace' place, should a similar situation occur again.
In an SBS, when talking about DF superiority and putting Magma > fire, Oda pointed out that DF superiority alone does not make a guaranteed victory. Which would be the most plausible fight to prove that? Aokiji vs the new holder of the Snow Fruit, if it gets found at all? Daz Bones vs. Baby 5? Machvise vs. Mrs Valentine?
Awakened fire + top tier ACoC may be able to do the magic of nullifying the advantage of magma.
That being said, Akainu vs Dragon is also an outcome I can see happening.