We [have]/[had] been friends up until this moment

In the first sentence there is uncertainity in the speakers' tone about whether he will continue the friendship or not and seems rhetorically interogative as if he is mocking John's act as being silly and unecessary but in a playful way, however, the second sentence shows that the speaker is definite on his decision about ending the frienship.

1. John and I have been friends up until this moment, but John has just stolen my wallet.

2. John and I had been friends up until this moment, but John had just stolen my wallet.

The present perfect refers to an action or state that existed immediately before the words were spoken (and may continue after they are spoken).

The past perfect refers to an action or state that has now finished: it is usual to use the past perfect to provide background and context.

If you want to make it clear that the friendship is over, you should say

We were friends up until this moment.

What you are proposing is a non-standard use of the past perfect, and it is only going to confuse people. Past perfect is used to make it clear that one action takes place before another action; and to put the present perfect into the past, as in the sentence

We had been friends up until that moment, but John's actions were unforgivable,

which implies that John's actions were in the past.