Without knowing the case specifics, I can't say with authority how likely this is to be overturned, but if Seagate can demonstrate that the project fell apart for business reasons that could not be reasonably anticipated, it'll die on appeal. And it is very likely that it will.
First, if Seagate could have established that the person was hired for a perfectly valid position, which went away as a result of business conditions they couldn't have forseen, then they wouldn't have lost this trial in the first place.
Second, the "At will" issue is irrelevant - the lawsuit was based on a law that says employers are not allowed to lure people into relocating unless there's an actual job waiting for them.
Finally, appeals are generally based on issues of law, not issues of fact. So unless Seagate can come up with a good legal argument why that state law doesn't apply in this case, it's unlikely they'll get a reversal on appeal. At best, they may get the award reduced.