It's a lot easier for a distro to update a default utility than to add a new one though. I suspect having updated curl would happen faster than adding httpie to the list of default utilities.
There's a happy medium, and we're not in it.
Most dependencies get updated much more quickly. It wouldn't even shock me if this change got picked up mid-cycle.
Curl is a command line tool. As long as they only add new functionality, there is very little that prevents an upgrade.