The GOP declined to adopt a new platform in 2020, deciding instead to stick with the language approved four years earlier. In essence, the party was saying that it would provide unconditional support to anything Donald Trump decided to do in his second term. It no longer had any principles other than standing with Trump.
If you want to attach a date to the MAGA takeover of the GOP, that would be a logical choice. Will the party do the same thing in 2024? Well, why not? Trump always likes to keep his policy options open as long as possible, and who at the convention is going to stand in his way?