There's still plenty of time for Madara to notice Sasuke. Even though Madara is wrapped up in his plan, there's still room for him to notice what's going on outside of his confrontation with Hashirama, and the combination of Naruto's BM and Sasuke's PS may very well catch the attention of Madara in the next chapter as Sasuke notably thought about Madara in this chapter.
I might have missed it but im kinda mad that the Madara hasnt even commented on Sasuke being there and having PS in all... and then that last combo.... like im not really a sasuke fan but i was expecting the dude to say something!
Yeah I still find that strange. There's no way in hell he shouldn't have been able to sense Susano'o at the very least. Madara of all people should know when an Uchiha hits the field.