Count me among those who think that, by the time Jon recovers from his wounds, the Night's Watch will be so changed the question of whether Jon's an oathbreaker or not won't matter much. The extent of the conspiracy to assassinate Jon isn't yet clear; for all us readers know, Bowen Marsh and his three accomplices, likely the men sitting with him in the Shieldhall earlier, acted alone. Certainly, knifing Jon in broad daylight, right in the open courtyard with wildlings, black brothers, queensmen, even the northern clansmen arriving in haste, seems a really, really bad idea that can only end in blood.
Referring to my post-ADWD OOB for the Wall
, should a melee break out between the NW and wildlings, the black brothers are almost sure to be outnumbered. Unless Marsh's prepared treachery for the clan chiefs in the Shieldhall, taken steps to secure the forty wildling hostages at Castle Black, or simply armed his faction well for conflict--stationing archers atop the Wall and towers, for instance, with orders to fire upon the wildlings at the first sign of trouble--the NW may not survive a fight with the free folk. In fact, Marsh himself raises this very concern when arguing Jon's decision to let Tormund through the Wall.
This is assuming Marsh has significant support amongst his brothers and/or decided to use force against Jon before the Pink Letter arrives, of course. Personally, I doubt Marsh's confided in the rangers, who make up about half the NW and have little respect for him, any plans to oust Jon. I can't quite imagine the builders or stewards Jon commands in ASOS against Mance Rayder being totally fine with murdering him either. Not to mention some might object to sworn brothers killing a second Lord Commander in as many years.
Furthermore, given that Jon announces his intentions to defend Selyse and Shireen from Ramsay Bolton, the queensmen are more likely to side against Marsh than with him even minus Melisandre's considerable influence, IMO. Flint and Norrey strike me as rather grudgingly impressed by Jon's handling of the wildlings; he reminds them of the ancient Kings of Winter. They may also dislike another Stark being betrayed to his death on principle, lol. What's more, supposing the conspirators succeed in quelling the wildlings at Castle Black, most of the adjoining forts are held by other wildlings, notably Oakenshield where the rest of Tormund's forces are staying.
In short: It might be no coincidence that, over the course of ADWD, Jon sends his most trustworthy and competent men away from Castle Black to other posts on the Wall. Marsh may actually have done Jon a favor by precipitating a bloodbath that'll allow the wildlings to kill or imprison Jon's diehard political enemies along with the worst useless dregs of the NW. If the surviving black brothers are either loyal to Jon or cowed by the free folk, whose numerical edge over the crows will be even greater, exactly who is going to oppose Jon remaining in command, marching to Winterfell, or doing whatever he damn well pleases? And, later, who's going to quibble over the NW oath if the entire North's in danger of being overrun by ice zombies?
On a meta level, I'd prefer to see the NW continue in some form because 1) dragons or no, a conventional military's needed to hold the line against the Others and 2) Jon would have no excuse to not immediately accept, say, the position of Rickon's regent or an offer of marriage from Dany if stripped of his vows. Jon's life and future choices are a great deal simpler when he's not chained to the NW, and I've no interest in making anything easier for him.