This AM heard that it will be 4 years before all the imaging data is returned to Earth. I assume the delay has something to do with power requirements and the 4 billion miles.
Did some homework.
Tx/Rx on X band.
Dual 12 watt TWTA Tx amplifiers.
New low power uplink receivers.
High gain antenna with reversible left/right circular polarity.
Two 8 Gig solid state memory storage recorders. One primary, one back up.
Downlink rate from Pluto was 1kbit/s per transmitter with a latency delay of 4.5 hours. But when power budget allows it, both transmitters can be used simultaneously in opposite direction polarities to double the downlink rate to 2 kbit/s. It takes approximately 16 months to download a full load of 8 gigs. So it looks like the average is about 1/2 gig a month. Decreasing the further it goes out.
Something else that takes time is that the instruments and camera are fixed, so the spacecraft has to be physically turned to aim them at a target. This in turn moves the antenna out of aim for transmission. So after the operation the spacecraft has to be physically turned back again to re-aim the antenna so that we can receive the signal downlink again. And the uplink latency is the same as the downlink latency to move it.
So I guess what it all adds up to is a slow run and patience on our end. lol
(As a radio guy I find the simultaneous opposite polarity thing VERY interesting)