I would actually put substantial money on a bet that the state will indict CA with or without KM's cooperation. Willie Meggs, the former chief prosecutor wasn't willing to pull the string, but GC is in charge now and she has more than enough evidence to indict CA (and possibly DA). Many prosecutors (including some from the Tallahassee office) are on record opining that they've achieved convictions in other cases with less evidence than they have right now against the Adelsons. I have no doubt that GC desperately wants more evidence, but I also have no doubt that she'll indict at least CA no matter what transpires. It's the right move morally and clearly the right move politically, given the public support for prosecution against the Adelsons.
Also, KM's own testimony under oath will be useful against the Adelsons in a future trial. KM's ridiculous claim that the cash deposits she made were all from tips can be soundly impeached now and her admission that her employment was a "favor" from Charlie also is significant. Furthermore, her assessment that she now believes CA was responsible for the murder was made under oath and is not hearsay. The defense will scream bloody murder, but there should be opportunities to publish that testimony in the next trial -- not as proof of CA's guilt, but relevant to KM's credibility. No matter what they say in public, I assure you that the Adelson legal team understands that the case against them is stronger now than it was before.