It won't really be an admission of "guilt" for a few reasons, one being that the "admission" won't fit the actual charges with which she's been charges. Also, counsel for the defense could poke holes into the Murder One theory, suggesting it might have been an accident and wouldn't be required to stand up and say "This is our position: Accidental Death", etc.
There were really 3 angles defense could have taken before Caylee was found:
1. Caylee is still alive. Defense would have probably tried to make it seem LE didn't follow up on legitimate sightings, might have even put on a witness that said Casey mentioned giving up Caylee for a private adoption and not telling Cindy, etc. In my mind, this would have been a tricky road to go down but a "winner take all" one. If Casey made a private adoption plan and suggested it was b/c she didn't feel equipped to be a good Mom and didn't think George and Cindy were the best parents (especially if Casey could insinuate problems there), jurors would have been very sympathetic to that (to the extent they believed it). Even if the private adoption didn't follow proper channels/laws. As to the adoptive parents...why wouldn't they simply come forward to at least say "Caylee's alive"? Odd, but jurors might buy the idea that they were protecting Caylee's location and identity no matter what. Key: this defense/position/suggestion is the only one that could explain Casey's carefree behavior, Bella Vida tattoo and total lack of concern (she knew Caylee was safe). I do think one juror (all that's needed) could have questioned the one hair in the car with the "death band", explained away the smells and air samples, and believed Caylee was still alive. Now that Caylee has been found, the sole defense that could have let Casey walk free is gone.
2. Accidental death. With the nightlife and lifestyle of this defendant, I'm sure nobody would have a problem believing Casey dosed her kid with anything at any time. The problem is.....none of her actions afterwards are consistent at all with an accidental death. They are in fact completely inconsistent with an accidental death. Even if your kid died accidentally....do you go and put on makeup, text your friend that you need a vacation, and go out dancing, laughing, smiling and having a blast? And the tattoo. And LE will put on a billion other things she did after the "accident" that will EASILY convince jurors beyond a doubt that when you see such behavior, then the death that preceded it was not "accidental." Even if a young mother was afraid she'd be thrown in jail b/c of the accidental death and therefore, hid the death....in this instance Casey shows no fear but rather, relief and jumps right back into the party life. Notice I didn't even add the tossing of the body in a garbage bag, passing the smell off casually as "squirrels", etc.
3. Someone Else Killed Her. This has the least chance of success. She's already sunk herself with the "Babysitter kidnapped Caylee" story. Not just b/c the babysitter never existed but because of her actions after the alleged kidnapping (see number 2 above) -- no matter who kidnapped her (babysitter, some alternate person such as a drug dealer she might try to pin it on, whatever).
I don't know why talking heads are saying defense will focus on forensics. All the forensics need to show is that Caylee is dead and they certainly do. If Caylee's poor withered body can't show what happened to her bones anymore, well then that's not prosecutor's fault but rather, the fault of Casey who hid the body in the woods. I still can't believe that Caylee has been found. I am so happy for so many reasons, including that it means Casey stays in prison for the rest of her life.