It matters not whether this is in the past, present or future tense, since Jesus is the third person of the Holy Trinity. Was in these verses implies was, is and ever shall be. Another way of saying this is truly, truly Jesus is the Christ.
Rev 1:8 I am Alpha and Omega, the beginning and the ending,saith the Lord, which is, and which was, and which is to come, the Almighty.
Rev 22:13 I am Alpha and Omega, the beginning and the end, the first and the last.
Act 18:9 Then spake the Lord to Paul in the night by a vision, Be not afraid, but speak, and hold not thy peace:
Act 18:10 For I am with thee, and no man shall set on thee to hurt thee: for I have much people in this city.
Act 18:11 And he continued there a year and six months, teaching the word of God among them.
Which was exactly what Jesus had commanded:
Mat 28:19 Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost:
Mat 28:20 Teaching them to observe all things whatsoever I have commanded you: and, lo, I am with you alway, even unto the end of the world. Amen.
1Jn 2:22 Who is a liar but he that denieth that Jesus is the Christ? He is antichrist, that denieth the Father and the Son.
1Jn 4:3 And every spirit that confesseth not that Jesus Christ is come in the flesh is not of God: and this is that spirit of antichrist, whereof ye have heard that it should come; and even now already is it in the world.
2Jn 1:7 For many deceivers are entered into the world, who confess not that Jesus Christ is come in the flesh. This is a deceiver and an antichrist.