The east side Anacostia Riverwalk Trail's bridge over the CSX train tracks (aka "Osprey Bridge") is open. According to a cyclist I saw when I was there last night, it's been open for a week. It's not finished - there are still some barrels and construction fencing up, but not across the entry points to the trail. This means there is now a continuous trail from Benning Road to Firth Sterling Road. You could make that trip before the bridge, but not without trespassing on CSX property - and the bridge is probably faster anyway.
Plus, the bridge is very nice. On the south side you get a great view of the Circle Fort Hills in Anacostia and on the north you get to ride up through the tree canopy. And because it's at more of a right angle to the railroad tracks, it's easier to watch trains than the Wetlands Bridge on the other side of the river is. There the bridge is at an angle such that the fencing makes look at the trains a little frustrating.
Where the trail from the bridge meets the NPS access road north of the tracks there is a nice little intersection with a short bike lane to let bikes and cars know which way to go. I didn't have my camera with me, so I have no photos but here is one of construction from DDOT.