I think it would depend on the circumstance. I haven't found any literature on your killing part of the question, so I'll answer that with some of my guesses, first. Killing another wolf uses up a lot of energy and I think that such an action would likely be reserved for, let's say, a territorial-related dispute over a relationship-related one. I think it's more likely that an outside wolf would kill a member of the breeding pair over one member of the pair killing the other because of internal conflict. On the subject of conflict within a breeding pair, I think the only thing that could cause conflict that could result in death is a scenario where there are advances on one member by a suitor either within or outside of the pack. If one member of the breeding pair was weak, would the other turn on that member alongside the better, stronger suitor? I don't know, but I would think (though I could be wrong) that territorial ties would be prioritized, first, and the suitor would be dismissed by whatever means unless the suitor was strong enough to thwart defensive actions and usurp the weaker breeding pair member. Again, whether the remaining breeding pair member would cooperate in the latter scenario, I'm not sure. If it did cooperate, I think that would factor into the abandonment part of your question, too.
I think the spirit of abandonment, and actual abandonment, is possible for wolf mates, but again, I do not have any solid answers for you.
Here is something I do know: it's a common idea that wolves are mates for life, but under certain circumstances, that isn't always true. Wolves will find a new mate if its mate dies; they are not tied to their mate forever in death. (That idea tends to anthropomorphize wolves. I know that's not what you meant by your question, but I wanted to get that out of the way.) They will mate with a newcomer if their mate has been usurped (-- and, through being usurped, that mate has been likely killed). I'm not sure if that fits your idea of abandonment.
On to stuff I'm less sure of. Occasionally, wolves who are "biders" may leave their pack but remain in pack territory and wait for their chance to breed, which generally means that a parent must die (and does that mean the other breeding member is or isn't a parent? Mech doesn't specify in "Wolf Social Ecology."
). Mech does reference a study regarding red foxes and how the "bider" strategy is perhaps the only way for weaker red foxes to get the chance to breed. If this was true for wolves, though, I'm not sure why one breeding pair member would leave the other for what is most definitely a weaker wolf than its existing mate. Outside of usurpers and biders, you might think that adoptees could play a role in getting a breeding pair member to "abandon" its mate, but according to Mech, most adoptees are 1-3 years old and non-threatening (as older, adult would-be adoptees are often killed), and, consequently, are more likely to go after maturing
members rather than matured
members. If an adoptee was targeting maturing/younger members and the adoptee itself was not an established member of the dominant breeding pair, I would think that the wolves that it mates with would be more likely to be temporary (because of their non-established status), and would be more likely to not mate with them the next year. But is that "abandonment?"
Anyway, while Mech and Boitani's "Wolf Social Ecology" doesn't provide any definitive answers for you, I think you'll find it a worthwhile read.