From an internet dictionary
discord
n [ˈdɪskɔːd]
1. lack of agreement of harmony; strife
2. harsh confused mingling of sounds
3. (Music, other) a combination of musical notes containing one or more dissonant intervals See dissonance [3] concord [4]
vb [dɪsˈkɔːd]
(intr) to disagree; clash
[from Old French descort, from descorder to disagree, from Latin discordāre, from discors at variance, from dis-1 + cor heart]
I've boldened the part that fits. The mane 6 are the representatives of the Elements of Harmony and discord means a lack of harmony. So therefore he is a natural and very fitting villian for them. But given the lighthearted nature of thee show I'm hoping he'll stick around like Q did and show up every now and then just to throw a monkey wrench into someones plans and cause mischief.
It would certaainly suck if we all got hyped up for him and he was gone by episode 2.
also yeah Discord has been discussed for quite a while now, like almost since season 2 was in rumored production. He was talked about on EQD, I remember Sethisto had a picture of a black Alicorn in armor and red eyes and below it read
I'll just assue this is Discord for now cause it's badass.
Which I think led many to hope and pray that season 2 was gonna be very grimdark, even me a little. But I gotta say I'm looking forward to the new season even more now that I know who his VA (Voice Actor) is.