I did it last Fall when the lake was at 3,624, and there was no real current to speak of after Gypsum.
This sort of depends on when you're doing your trip. The ramp at Hite is usable down to 3606. Today the lake is at 3,615, and it's been dropping an average of a tenth of an inch a day. So by the time the lake gets to about 3,600, there should be moving water in the vicinity of the ramp on river right above Hite. This will all change in the late Spring, when the runoff starts bringing the lake up, of course.
For current updates, you can see lake levels here
Lake Powell Water Database
Hope this helps you figure out how far you're going to row if you don't have a motor.