If they stick to the rules, Cruz and Trump will be the only ones allowed to compete at the convention for the nomination, with majority of delegates in 8 states (Cruz is pretty likely to make it to 8 or 9 with Kasich in, many more with Kasich out). Even if they roll back the requirement to 5 which it was before, they’ll still be the only ones.
Four right now, correct? Utah is a BIG one for Ted. If Kasich denies him that one, well, that will leave a mark at this point in the campaign. Your statement would automatically be edited to 7 or 8, ouch. Pretty iffy.
But an online caucus? You would have to put that into the bag for Cruz, right? No way he isn't going to win that small of a caucus style deal, I think he will get this one done with Mitt's help. For the record, Cruz was smart to accept Mitt's "endorsement" or whatever it was, Utah is too important to him as a potential 40(b) state.
However, if nobody achieves a majority on the first ballot, I believe Rule 40b goes by the board -- and anybody can be nominated.