Older release dates don't count. The next DVR is expected to be a combined DirecTV/Uverse box, probably a server only with clients. Same config as the HR54/C61K for 4K.
I'm going by memory, so these times maybe a month off.
The HR54-500 was released to select DMA's in late July or early August 2015. HR54-700 in December. And HR54-200 in February.