The soon to fly Boeing 767-2C/KC-46 will have both center boom and wing mounted probe and drogue.
At least in theory it'll be capable of fueling 3 aircraft at the same time.
I have an interesting 1965 photograph of a newly converted Victor K1 with two Lightnings in contact. The picture is a wirephoto which has been sent to a US Press agency, and the text comments that the tanker will be able to refuel three aircraft simultaneously!
Thats always been theoretically posible with 3 point tankers, but would involve some pretty scary formation flying. I'm wondering if it has ever been done, if only as an experiment or trial?
Re rates of flow - these are certainly dependent on the receiver as well as the tanker as has already been stated - thirsty F4s and Buccaneers were always a welcome sight as they could gulp our fuel much more quickly than, say, Lightnings.