I just finished the 'DEAL' ending of GTA IV for the first time. I went up to the safehouse save the game and Kate called me, and we went on a date. Later, I called Kate and we once again went on a date. I was always told (and have read on various forums) that Kate will no longer have contact with Niko after the story because she couldn't respect Niko's decision to take the money..
Also, Francis still appears on my mobile phone, but I killed him a long time ago.