As for the EoF expansions and Enchanced Edition:
EoF is the contentents patch that will be released on the 30th of November - for all users (new, pre-orders). Even if you don't have it installed or registered, you will get it just like any patch as soon as you start the game.
After the 30th of November, Sword of the Stars II: Lords of the Winter will be no longer available. Instead, SotS II Enhanced Edition will be sold, containing Lords of Winter and End of Flesh.
So basicly, if you buy now or later, you get the EoF, but I cannot say anything about any price changes between SotS II: LoW and Sots II: EE.
For reference, please head to the Kerberos Productions forum - there you can find a largish topic bout the EoF and EE.
Hope this helps