Carl Icahn on CNBC said he believes a separation of eBay (EBAY) is "not if but when." Icahn likened eBay at current levels to his profitable initial investment in Netflix (NFLX). The investor still thinks eBay is undervalued. Earlier today, Icahn ended his proxy fight with the online auction site. Shares of eBay are down 2% to $54.79 in afternoon trading.