Green Bay would never trade Rodgers to the 49ers unless they gave up most their defense and Kittle, even then with the deep contempt between the franchises and both in the NFC I doubt it would happen out of spite against Rodgers wanting to leave the promised land and the Packers thinking what AFC team can we fleece and put Aaron in the worst situation.
Broncos and Raiders have been mentioned, Raiders and Gruden that's a possibility, Elway would love Rodgers there, but they just traded for Bridgewater. Still Bridgewater could be moved again to someone.
Jets, Texans, Bengals are probably the least favored at this point to be challengers.