What does this mean?
Your application to Michigan State is still under review. Due to increases in the quantity and quality of the freshman application pool for the fall semester, our office is carefully monitoring space and conducting thorough examinations of all fall semester applicants. Although no new information is available at this time, you will receive a decision on the status of your application by mid-April.
It means that you won’t know if you were accepted to Michigan State University until the middle of April at the latest.
Are my chances of getting in unlikely
It looks like about MSU’s yield of accepted applicants who enroll is around 40%. I would guess you have a decent chance as some students who are ahead of you decide to go elsewhere.