I think are is the usual, since ' the next few days ' is so obviously plural, but it really depends on how the speaker is envisioning the subject-- several individual days (ARE) or a single period of time (IS). Days is no special case-- the same argument could be applied to any unit. The last two days have been the happiest of my life.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.