Here are some thoughts for this current discusison:
1) I am unsure about the masses, but I am aware that in the last 10 yrs or so a great many theologians in the ELCA and some of rather honorable mention (such as Joroslav Pelican for example) have left the ELCA not for more conservative Lutheran denoms but for the Catholic and Orthodox church. Whether this reflects the direction of the exodus of the laity I am unsure of.
2) Should the ELCA split, the nature of the split will likely depend on the size of the split. If only the really conservative and Word Alone churches leave, then they will likely just form some independent denom and do things pretty much as they are except consider themselves "free" from the title and stereotypes of the ELCA. They will turn around, not look back, and want nothing more to do with their former synod, or at least want as much to do with them as the LCMS for example would want.
3) If however there is a great split, say closer to 50/50 for example or at least some noticable size, one that includes many of the conservative leaning moderates, I would venture that the bodies will be in rather close. I would guess that they would be in full communion minus the exceptions: one would be something like, practicing gay pastors of the ELCA would not be permitted to "cross over" so to speak in pulpit swap type stuff. That is what I would presume, a close but distinctly seperate group.
4) One thing to discuss that I am unsure how it has been thought out by many is the pension issue. This for example has caused some LCMS pastors I am aware of who did not leave at seminex and later wished to to stay in the LCMS, because your pension is bound to your synod. If churches leave the ELCA, they will be responsible for supporting the pastors they take with them. And with all respects, Lutherans in general have been short on giving and horrible at talking about money in the church of late. As one woman I know who is a board member of one of the ELCA seminaries put it, "Lutherans often act as if money itself were a dirty thing." So many churches right now, especially now in our economic times are struggling to stay open, to take on the burden of their pastor's pension may be just too much. Yes money is not everything, and yes they need to follow where they believe the true witness to the gospel is, but it is irresponsible to leave pastors in financial insecurity.
pax