If that happens, the math for Trump to avoid a floor fight becomes more complicated. At that point, almost all of the winner take all states that follow will have to go to Trump in order to lock in enough delegates for the first round vote.
The strategy is for Cruz, Rubio and Kasich to win their home states Any loser drops out. To take this to a brokered convention Florida and OHio cannot go Trump. Otherwise momentum and time favors Trump. If Rubio wins Florida and Kasich loses Ohio then Rubio is the GOPe candidate. If Kasich wins Ohio and Rubio loses Florida then Kasich is their last hope.
Cruz could win Texas and Kasich and Rubio lose but they will still not back Cruz. Romney will jump into the race to be the party savior hoping he can win enough of the remaining states to go to a brokered convention. The other alternative is to get Romney on enough state ballots as an indecent in the general election to ensure Hillary wins. In any scenario this is the end of the Republican Party if they do not support Trump if he is the leader going into the convention.