I went onto the Belt Parkway bike lane to see if any progress was made at Plum Beach, and they are working on it. My mother, who happens to live in the building that overlooks the Belt, reported that trucks have been unloading boulders along the shore, and they actually have built a dune to protect the bikeway and highway along the exposed area. There are grasses planted along it also. The bikeway itself is still not built, but looks to have been cleared of sand in places. Maybe they'll be doing that soon.
In any case, you can walk it as it isn't that long. I was there on a Saturday, and I don't know if there is construction on weekdays. Plus the shutdown probably slowed them down as it is an NPS run facility.
I have some pictures on my iPad, but I don't have that with me at the moment. I'll post them later.