Spoken in the Same Breath
    In this scripture, the Lord Jesus is teaching the disciples about the Holy Spirit who will come into the world. But included in this teaching is His statement that "for he dwelleth with you" which is in the present tense. The God that was dwelling with the disciples was the Lord Jesus Himself. Then Christ states of this Spirit "and shall be in you." which is future tense.

    The person the Lord Jesus Christ is speaking of is Himself, yet which will be in yet another manifestation to the disciples... the Spirit of God indwelling them. This is fully congruent with Christ words to the disciples just prior to His ascension into Heaven that "I will be with you alway, even unto the end of the world." He certainly would be, in the form of the Holy Ghost.