Too late, but, hopefully, they’ll change it back.
I agree this is, at best, a curious design choice. I’d very much like to hear the developer’s rationale. @bsmith, might you be available to provide insight?
Please no new command either. There’s already a Send option right next to the text box. The return key need not duplicate that functionality. Changing it back would also harmonize the iOS interface on iPad and iPhone. On iPhone, the return key behaves as one would expect and does not send.