I checked 25+ translations and about half uses "is" the others use "has".
I expect it's the famous aorist tense, (was is and keeps coming) but I don't have a translation that make this clear.
Well that's abit of alie.... I have a homemade online translation that show aorist tense. I don't really trust teh translation. Anyway according to that translation lots and lots of words are aorist. It has great consequences; for example it means that the whole book of Revelation is happening for nearly 2000 years.
It is easy to figure it out by just looking at the other scriptures. Jesus said, where I go you cannot
come, I go to prepare a place for you, in my Fathers house
are many mansions (The fathers house in not upon the Earth but in heaven)
Jesus is saying that he is in heaven, and none of his disciples could go and see him, but I will not leave you comfortless I will send you another
, notice he doesn't say I will send myself again.
If he's in heaven as stated then John is talking about those who deny Jesus has
come not is
come, otherwise the words about Jesus sending another comforter are also wrong, also the words about Jesus in heaven also wrong, if that is true then the bible is becoming weaker and that is not good for the faith.