Although it is quite premature my thoughts would be that existing shareholders would not get shares automatically in the IPO. A recent example of this would be SGI's spin-off of MIPS. Existing shareholders get the benefit from the cash raised and returned in form of dividend to parent and the future income of the new company through the remaining ownership.
B&N can structure the spinoff/IPO in whatever manner it thinks will generate the most value for BKS shareholders. (That is the ultimate purpose of this whole endeavor, at bottom.) Current shareholders may or may not receive shares in the new company; my guess is that we will. (When AT&T spun off Lucent, T shareholders received a proportional number of LU shares -- that sure turned out to be a sweet deal...) Basically, we will all have to wait until the IPO registration is filed -- all the details will be set forth therein.
Someone asked about the new company's ticker symbol -- there ain't none, yet. But I assume that the spun-off company will be traded on NASDAQ, not NYSE.