We reported last night that Missouri may take a while on the Republican side. Essentially, Trump is ahead of Ted Cruz by about 1,700 votes, or .2%: this is enough to permit a recount, not to mention requiring the state to get a move on counting the provisional and absentee ballots. So, no call on the Republican side. The problem for Missouri is that they have the exact same issue on the Democratic side: Hillary Clinton is ahead of Bernie Sanders by about... 1,500 votes, or .2%. So counting all of those provisional and absentee ballots will need to take place, not to mention the question of whether Sanders will call for a recount.
So, just in case you were wondering if anything was ever going to be simple, this election cycle: no, probably not. don't know if this happens all this often - in fact, I cannot personally remember the last time that both of a state's primaries were this close. I am reasonably sure, though, that Missouri is going to have delays in the process, given that the state will be trying to do two extremely similar, yet distinctly different, tasks at once. And there will be mistakes. Be prepared for that right now. It's not because of any conspiracy, it's just that the system will be trying to handle an already-nonstandard situation that has suddenly became a lot more complicated than expected.
PS: At a guess, it won't be decided today. CNN noted that absentee overseas ballots will be accepted until noon on Friday; normally the margin is enough that such things aren't likely to make a practical difference, but there is nothing normal about this election cycle. Assuming nothing changes, you might see the race called Friday afternoon. Or next Monday. If we're lucky...
PPS: On the issue of the recount itself: Ted Cruz should request one because Cruz can still win the nomination, and thus needs every delegate he can snap up. And Bernie Sanders should request one because Sanders cannot still win the nomination, and should thus just waste everybody's time on the Democratic side. In both cases, in other words, and to use the cliche: every little bit helps.