HSA is going to need a new 5K Commander soon.
It's too big of a jump for So Sui, so I could see a new officer joining, or Ma Ron assuming that slot.
Saki clan only sent 10 people this time, but I can see Io becoming one of Shin's lieutenants. Could easily imagine she'd be curious to see why Kan Ki took such a liking to him, if she doesn't already know.
I don't think they actually matter much when it comes to leading during an actual war. Ouki's vassals weren't generals during the Bayou arc, hence always addressed as commander and never as general iirc. But still led thousands of people.
Even in the HSA, technically, Suugen is in charge of more than 5k+ troops already as the infantry commander (which should make up more than half the army), even though officially he only has 1k in his "unit". And the likes of En-san/Sosui/Kyoukai automatically have command over the entire HSA due to be Shin's LT. even though their positions are only 1k-5k commanders.
For the LT. I don't think we'll ever get any more LTs. for Shin, since they're essentially the right hand men.
EnSan - trained as Shin's right hand man in that secluded zone so got that position.
Kyoukai - cause of the dankan battle
Sosui - due to respect for that dude who was killed, and later served a crucial role in keeping the unit intact when Kyoukai left
Why even Karyo Ten doesn't have the role of a LT. despite doing so much already. So the LTs. imo are all set, and it's just gonna be the commanders/vassals who'll be out.
Just my opinion though, liked the topic so figured to comment.