It's very strange.
He said Sasuke should come when he has MS. Which implies that he needs to take MS eyes to gain the perfect MS.
Because if just taking the normal Sharingan is enough, why tell Sasuke that. To beat Sasuke and take his eyes when he also has MS is way harder, than to just beat him and plug his eye when he doesn't have it.
Itachi is probably very desperate, because the time when the light leaves his world is near.
Which is somehow sad. Because it means he'll get beaten/killed now.
"For Feanor was made the mightiest in all parts of body and mind, in valour, in endurance, in beauty, in understanding, in skill, in strength and subtlety alike, of all the Children of Illuvatar, and a bright flame was in him"