The other poster made some great recommendations for place to stay. If you are seeking luxury at the level of Four Seasons, there really is only one show in town. That will be Mwiba Lodge by Legendary Expeditions and they are located in a massive private concession in the southwestern sector of the park near Ndutu. In addition to witnessing the migration, this private area will afford you great cultural interaction with the Maasai and Hadza people in addition to walking safaris amidst the migration, night safaris in search for nocturnal species and off-roading when you spot a high profile animal away from the road network. Four Seasons is considered downtown/central Serengeti or Seronera area and it will not be optimal for the migration this time of year. If Mwiba Lodge looks too robust/substantial, they do have a high spec simpler tented affair called Mila Tented nearby. They also have a luxury mobile safari rig with real showers and plumbed bathrooms in a neighboring concession. With that said, Feb carry some heat and Mwiba is one of only handful of lodges in the Serengeti with air conditioning (Mila Tent and mobile safari does not have AC). I checked with Legendary Lodge and all of these properties are scheduled to be open on Dec 1 or Jan 1.