Yes, it is still way early, and the Republican convention a long time away. However, the question that is arising is whether it is still possible to stop Trump -- and if so, for how much longer will this be true?
Let us suppose, for the sake of discussion, that nobody actually "stops" Trump. That is, he arrives in Cleveland with a plurality of the convention delegates -- but only a plurality, not a majority. That means, for Trump to get the nomination requires that, after failing to win on the first ballot, he needs to win over at least some of the delegates of other candidates. On the other side, beating Trump for the nomination requires some other candidate to collect almost all of the delegates from the other candidates.
The question becomes: which scenario is more likely. Or, to put it another way, which candidate has made the nastier attacks on the rest of the field. How negative are the delegates on those other candidates who have been trashing their boy?