Based on information provided by your DS in his summer application program, USNA has deemed him to meet the minimum requirements required to become an official candidate and open the portal for him to begin his formal application-which has many steps.
No one on this forum can tell you if your DS has a good chance of getting accepted or not-only the admissions board makes that determination and there are several qualifications that need to be met in order to be considered fully qualified to compete for an offer of appointment.
Some outstanding candidates may be offered letters of assurance, or even receive early appointments but the majority come after the application closes in Dec.
It's a great journey and you and your DS will learn more than you can imagine going through it.
Complete application steps EARLY, put together the BEST package you can and work hard to make yourself stand out. Navy has to want you as much as you want them.