Jennifer Lopez is casting doubt on whether she will return to American Idol next year as she juggles motherhood with a comeback in both her pop music and acting careers. Lopez, who has young twins, told talk show host Ellen DeGeneres this week that she wasnt sure about renewing her contract as a judge on the TV singing contest for a third year. And on Wednesday, sources close to the singer told E! News that she was just too busy and was planning on calling an end to her time on American Idol. Now this is my second year - I dont know if I can go for a third year. I miss doing other things. It really does lock you down, which was nice the first year with the babies being three, but now theyre getting more mobile, theyre about to go into school ... So I just dont know, Lopez told DeGeneres on Tuesday. Fox television, which airs the popular show, declined to comment. But Idol executive producer Nigel Lythgoe told celebrity website TMZ that the show wanted her back. Lopez made similar noise...