[Petronski]

It is past tense, but not the end of the verse. Read it like this: Do all I have commanded you and I will be with you to further command you until the end of the world.

Ah, but Haydock puts it better than I ever could:

Jesus Christ will make good his promise:

1. by always dwelling in the hearts of the faithful;
2. by his sacramental presence in the holy Eucharist;
3. by his providential care, and constant protection to his holy Catholic Church.

These last six lines of St. Matthew's gospel, says the bright luminary of France, Bossuet, most clearly demonstrate the infallibility and indefectibility of the one, holy, Catholic Church, which all are commanded to hear and obey.

[Always Right]

It is past tense, but not the end of the verse. Read it like this: Do all I have commanded you and I will be with you to further command you until the end of the world.

Yes, as a Catholic you would have to read it that way, but that is not how it is translated. Assuming the English interpretations are correct (KJV, NIV, etc), it seems conclusive that Jesus has already provided the apostles all things to be taught, and BTW He would always be with them.