I think RDI will do a lot to help with this, and you will probably see a broadening of his awareness through both that and the Floortime. I would also talk to his SLP and OT to see if there are any new things you could try at home. Some kids do better with social conversation and interaction in the middle of physical activity, like an adult pushing them in a swing, or after a period of sensory activity.
One trick they had us use with dd was to try and change her routine or be deliberately silly. Never to the point of really upsetting her or causing meltdown, but enough she had no choice but to notice it. Things like putting shoes on hands, instead of feet, or putting on a coat and then offering a sweater. (DD was very clothes-motivated at this point, lol) The goal is to wait, see if your child comments by gesture or word, and if they don't, model and guide them through how to talk about it. "Uh-oh. Shoes go on feet! Silly Mommy!"
I think it's also tough, but important to remember that all kids, our SN kids especially, have times where they do stall for awhile, and take in all the skills they have learned. It can be tough to tell if this is a natural pause, or an issue that needs to be addressed therapeutically. DD sometimes, to this day, becomes much more prone to meltdowns right before she gains a big new skill.
It's late here, so sorry for any errors or babbling!