There are two things I thought too obvious to say; but perhaps they do need to be said.
(1) Although the Fathers, and the Byzantine Liturgy, do sometimes talk about Church superseding Synagogue, I think this may, in the very strictest pedantry, be anachronistic. Historically, Synagogue Judaism and Eucharistically Sacrificial Christianity both emerged from the period 33-70 A.D., after which, of course, Temple Judaism was an impossibility. In terms of simply historical narrative, neither religion is, strictly speaking, the "Father" or the "Elder brother" of the other, however attractive such language may be diplomatically.
(2) Supersession most certainly does not mean that Gentile supersedes Jew. The man who has Faith (whether Jew or Gentile) supersedes the one who does not have Faith (whether Jew or Gentile). As S Paul says on page after page of Romans, God has bracketed both Jew and Gentile together under Sin, so that both equally need and can receive Mercy. Nor does Supersession mean that Gentile is better than Jew, or that Jews have some inherent inherited defect from which Gentiles are free. They don't.
And a personal note.
I have never, in the course of my life, done the Holy Week liturgies in any form other than the Novus Ordo forms. Further: I have never even attended the older rites. My only motives for getting involved in this question are: a feeling of outrage about a matter of principle; a more general sense of unease about those who, in various areas, seem keen to demolish what was Magisterially established or confirmed less than a decade ago; and a personal disgust at those now jumping onto a let's-trash-Ratzinger bandwagon.
And a philological speculation.
If the term Supersessio upsets some people so much, why don't we offer to use instead some other word from the rich vein of terms used by S Paul in Romans Chapter 11: apobole, perhaps, or apotomia, or exeklasthesan [thrusting away; cutting off; they were broken off].