If one would get a decision, would it be only acceptance/rejection or could there also be a deferral?
I found this from http://news.harvard.edu/gazette/story/2014/12/977-admitted-to-class-of-2019-under-early-action/
“In addition to the 977 admitted students, 4,292 were deferred and will be considered again in the Regular Action process, while 541 were denied, 19 withdrew, and 90 were incomplete.”
So about half the class was admitted SCEA, and a very large number of students were deferred. Deferred means that those 4,292 students were moved on to the regular decision round to be accepted, rejected, or waitlisted. By looking at the numbers you can see that the vast majority of SCEA applicants were deferred. Good luck! 
Sorry, so what is the difference between a deferral and a waitlist?
SCEA applicants can be deferred to the regular decision round. Those in the RD round get accepted/rejected or offered a spot on the WL.
A deferral is where they don’t make a decision on your application in the early round, but defer their decision to the regular round. The message to take from this would be that you’re good enough that you might get in, but youre application wasn’t absolutely compelling.
To be wait listed is to be told that at the end of the regular round you’re still not being offered a spot, but if spots open up because an unusually high number of accepted applicants choose to not attend, then you might still have a chance.
sherpa’s answer is MUCH better than mine!!!
…Or that you’re an international and they want to compare you to your country-mates/ other international students.