It is plentiful today, but supplies can change quickly. In Pittsburgh it seems that most sources are out, even though the flu hasn't really hit hard yet. The only source is the Allegheny Dept of Health. Some said they had supplies through the end of the year, but the supplies seemed to be several thousand doses. However, yesterday they set a record of 761 doses dispensed, which was probably broken today. Tomorrow they are moving to a larger facility and all three networks carried the story today. I suspect that the supplies that were good till the end of the year will be gone by the end of the week. Most in line were young children, so many will be coming back in a month. I suspect this will be repeated throughout the country, especially in the east, where the flu is just taking hold. Thus, the "plentiful" flu-mist may not be plentiful for very long.
I did a google news search on flumist and got about 1000 hits, with 250 of the hits in the past 24 hours. Its pretty easy to see that the 4 million remaining flumist doses will not last long.