The rules for the upcoming convention haven’t been written yet. The newly elected delagates from Trump, sCruz and Kasich will make up the bulk of the rules committee members, they will write the rules for this convention.
To be more precise, tentative rules for this convention have been written. They can modify the rules, but too big a change would look corrupt. As for the "newly elected delagates from Trump, sCruz and Kasich", first, as a Trump voter, I'm hoping the Cruz voters will vote Trump in November. I'm not convinced that fighting with them and insulting them is the best way to earn their votes. Second, those newly elected delegates are in most cases bound to Trump, Cruz, or Kasich, but that does not mean they actually support their candidates. We (voters in general and the Trump/Cruz campaigns in particular) have to watch them very carefully as they write the rules and at the convention.