The Nost experiment was about technical feasibility and strength of customer interest. And feeding that back to Blizzard.
What can they do without Blizzard taking on legacy?
A. They don't want lawyers coming down on them, so running further servers themselves is probably out of the question unless they want to live in Russia rather than just have a server based there
B. The community [or "someone" anyway] could develop a legal vehicle and business plan to meet Blizzard IP concerns and allow private servers to operate [which I'm guessing is something the Nost team are not geared up to take on as I assume they are IT experts primarily, plus it would require a lot of money, or luck in finding amenable lawyers etc who will work for free]. Incidentally I wonder whether some open source group or one of those university-based software preservation teams might be interested in an angle in this; could make for an interesting project as it exposes the practical problems already looming with increased on-line, server-based gaming of all kinds, only in this case it also involves the preservation of a virtual world [or maybe that should read "history of that world"].
C. Or they could feed back the code/database fixes into mangos and let others have a go [been raised before, probably feels like abandoning the project, and maybe hard to do without infringing Blizzard IP anyway?]
The problem here is knowing how long to wait before we can conclude that Blizzard aren't going to do anything regarding legacy and that it needs another initiative [this time legal + business model rather than technical] from the legacy community.
Unfortunately the ball has been put in Blizzard's court and I'm afraid that they could reasonably take a year before giving any indication of action [I wouldn't expect anything for the next year at least, with Legion due out], and after that it could easily be a further year before anything appears. And if nothing appears then, that's two years wasted in the legacy community.
In the circumstances, the appropriate next steps might be C now, followed by B in a year's time if there is no sign of legacy-oriented activity by Blizzard.