Nestle-Aland has NEVER been the Majority Text. The Majority Text means something very specific - that reconstructed text based on which readings are attested to by the majority of Greek manuscripts, whatever their age or type. Now, it's not always possible to have a 'majority' reading, and so most texts that purport to be a reconstruction of the Majority Text usually contain a couple of minority readings that have to be arrived at by means other than simply totalling up the manuscript support for each reading, but there is a pretty clear 'Majority Text' that emerges from this process, as distinct from the Critical Texts and, to a lesser although still significant extent, the Textus Receptus.
The Nestle-Aland text is what is known as a 'critical text', because it attempts to find, in so far as is possible, the earliest readings at every point in the text. Every individual reading is examined in light of the external evidence (which manuscripts a given reading appears in, the age of those MSS, comparison to other MSS with similar and different readings) as well as internal evidence (trying to discern the reasons for changes in the text - are the reasons theological? liturgical? typographical? visual? Are they deliberate, or accidental?).
The majority of textual scholars would hold to something like the NA text (perhaps with some caveats here and there, but based on agreement that the underlying methodology is sound), as do the majority of seminarians, pastors, bible translators, etc, so I suppose in that sense it is a 'majority' text. But so we're clear, that is NOT the sense in which I talk of a Majority Text.
