Missouri won't be in the basement of the SEC just won't be a factor. They will have a smaller role than they did in the big 12 where they have not been very successful either. But the SEC doesn't care about their athletic program as much as it cares about the TV markets it represents and St. Louis and Kansas City are a nice qddition.
Yes playing MU was always a great rivalry and I remember being late to dances in high school because I waited for the game to be over. Yes I attended KU and a lot if my family attended MU, still don't feel the need to ever play MU again unless they stay a serious competitive team and we play them in an early tourny like we do Duke or Kentucky. By MU have fun being irrelevant in the south.