According to Zenit, a group of cardinals are asking other Roman Catholic bishops worldwide to join them in petitioning Pope Benedict XVI to proclaim a new Marian dogma which would “proclaim the full Christian truth about Mary” – namely, that Mary is “the Spiritual Mother of All Humanity, the co-redemptrix with Jesus the redeemer, mediatrix of all graces with Jesus the one mediator, and advocate with Jesus Christ on behalf of the human race.”
Vox Populi Mariae Mediatrici is an entire website devoted to a new Marian dogma.
My impression is that the Orthodox in general would have less of an objection to the actual content of the proposed dogma. Mary’s role as our spiritual Mother, intercessor, and pivotal figure in the drama of the Incarnation is already quite apparent in the Eastern Orthodox tradition, not to mention the Western Catholic tradition (why then, if these concepts are already well-represented in the Tradition, would we have to have a dogma proclaimed?).
But from the perspective of ecclesiology (in my opinion this is where the real chasm between East and West still lies), I believe that this unilateral action would put the cause of Orthodox-Catholic rapprochement back several centuries. The very act of the promulgation of the dogma by the Pope, assuming as it does the ecclesiological propositions of Vatican I, would be the bone of contention.
The whole idea also betrays a very modern understanding of the very nature and purpose of dogmatic formulations within the Church. See Hieromonk Maximos’s comments (here and here) on “dogma as tragedy” (and note the reference to Dr Mark Miravalle, who happens to be a major champion of the “new dogma”).
Of course, this campaign has been around for quite a while. My guess is that Benedict XVI, like his predecessor John Paul II (a very “Marian” Pope), does not see the wisdom or the necessity in making such a proclamation.
Orthodox and Catholics have enough to hash out concerning primacy and infallibility in the Church, the procession of the Holy Spirit, the Immaculate Conception (and depending on who you ask, there are many more issues that need to be settled). We’ve come so far, and we have a long way to go. Let’s not add another disputed topic to the list!