I assume you mean Trump will have all the delegates he needs by then. Probably. But read Cruz's words again, please. He is saying IF Trump doesn't have them (hint: "hat's what "neither he nor Trump secures enough" means).
"...in the event neither he nor Donald Trump secures enough delegates before then..."
Are you saying that if Trump doesn't have enough delegates they ought to dismiss the rule and give it to him anyway? That sounds like a brokered convention to me, and I don't support it whether it goes FOR or AGAINST Trump.
Honestly, I don't know what the details of the rules are, but whatever they are, they should be followed in a fair and impartial manner. I am certainly not suggesting that any rule be dismissed for anyone, and I am perfectly sure that Cruz is not suggesting any such thing either.
So, if the Convention arrives and none of the candidates has amassed the magic number of delegates, what happens? The nominations are made, a vote taken, no-one wins, and the contested convention begins. That is all that Cruz is saying, it seems to me: it is nothing more than an objective statement of the facts. I certainly see no reason for the Trump folks' hand-wringing and pearl-clutching.
Fair disclosure: I favor Ted Cruz and think it likely he will have more delegates than Donald Trump by the time of the convention, but I am far from certain that he will have sufficient delegates for a first ballot nomination. I'm pretty darned sure Trump won't. What happens then? I don't know, but this nomination does not belong to anyone by right. I hope that someone has all the delegates required to ensure a first ballot success, but we will have to wait to see how this plays out.