Blood of the New Covenant offered to whom?

context

Luke 22:15

And he said to them, "I have eagerly desired to eat this Passover with you before I suffer.

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Luke 22:20

In the same way, after the supper he took the cup, saying, "This cup is the new covenant in my blood, which is poured out for you.

Matthew 26:28

This is my blood of the covenant, which is poured out for many for the forgiveness of sins.

it is extended to mean all of humanity, however Luke's word choice of you (pl) however refers to the apostles here, contextually. The you, ὑμῶν (humon), is 2nd person genitive plural.

Jesus intended that the "Lord's Supper", as a sacrament or ordinance of the Christian church, be enacted wherever Christians gathered together in worship.

We know this, in part, because God revealed it to Paul after his conversion to the Christian faith.

For I have received of the Lord that which also I delivered unto you, that the Lord Jesus the same night in which he was betrayed took bread: And when he had given thanks, he brake it, and said, Take, eat: this is my body, which is broken for you: this do in remembrance of me. After the same manner also he took the cup, when he had supped, saying, this cup is the new testament in my blood: this do ye, as oft as ye drink it, in remembrance of me. For as often as ye eat this bread, and drink this cup, ye do shew the Lord's death till he come (1 Corinthians 11:23-26).

The word you, which the Lord used in referring to the disciples gathered with him in the upper room just prior to his death, Paul also used in addressing the Corinthian believers, most--if not all--of whom were not part of Jesus' inner circle of disciples on the night he was betrayed.

In context, Paul was writing to the Corinthians to underscore the seriousness with which they were to enact the Lord's Supper. Evidently some of them were turning the agape into a drunken food fest, not discerning the Lord's body (v.29b). Paul reprimanded them for the impious way in which they were desecrating something holy, and he warned them of dire consequences were they to continue their impious ways (see vv.27-31).

A biblical answer to your question requires broadening the context of what Jesus said and did in a particular situation to a particular audience to include other situations and other audiences, right up until today.

Christians who name the name of the Lord today and who celebrate the Lord's Supper as an important (if not the most important) ordinance/sacrament of the church are (as were the first disciples, apostles, and first-century Christians) "covered" by the same blood which Jesus poured out at Calvary.

If we say that we have fellowship with him, and walk in darkness, we lie, and do not the truth: But if we walk in the light, as he is in the light, we have fellowship one with another, and the blood of Jesus Christ his Son cleanseth us from all sin. If we say that we have no sin, we deceive ourselves, and the truth is not in us. If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness (1 John 1:6-9 KJV, my emphasis).

And he is the propitiation for our sins: and not for ours only, but also for the sins of the whole world (1 John 2:2 KJV, my emphasis).

In conclusion, yours is not so much a truth question as it is a context question. The Scriptures make clear that the blood which Jesus shed at Calvary (the blood which "the cup of salvation" signifies) was poured out for all humanity in general, and for Christians in particular, since they alone experience the joy of sins forgiven.

The 11th century Byzantine commentator, Theophylact of Ohrid, who wrote a comprehensive commentary on the Gospels compiled from the writings of earlier Church Fathers, wrote:

When the Lord says, which is given for you and which is shed for you, He does not mean that His Body was given and His Blood was shed only for the Apostles, but for human nature itself. Therefore, whenever He says, Given for you, understand it to mean, "Given for the human nature which belongs to you all." (An Explanation of the Gospel According to St. Luke)

I think that one could say that this interpretation is also reflected in Matthew's and Mark's accounts, where they recall Jesus saying which is shed for many:

Matthew 26:28

For this is my blood of the new testament, which is shed for many for the remission of sins

Mark 14:24

And he said unto them, This is my blood of the new testament, which is shed for many