I doubt it mate. Sponsors would always be attracted to United because of it's huge fan base. And that is not something that will change with one poor season or for a long time
One season, no. Three dry seasons? Its a real possibility. Whatever plan they had for Fergie leaving, I'm sure it didn't involve transition longer than 3 seasons. LVG will most likely get to run out his contract, but my bet is they expect at the very least a very serious title challenge and strong showing in Europe.