Future Single Target NP Servants

Hmm for sabers there's Musashi coming in January and Sigurd who's coming in two years.
There would probably be Jalter banner which would be best for ruler bosses.
For assassin's then King Hassan would be top tier and.comea after Musashi.
Right now there's two NP spammers with Tamamo lancer (best for male Archer bosses) and could use her NP continuously with supports due to her high rank class skills and the monstrous Altria's Archer who could spam her NP like crazy with supports, and drain bosses NP gauge with a 70% probability.
For riders there's quetz if you missed Ozy though not as great as Ozy she comes with a targetable guts and buster buff, high level charisma and crit damage boost, so as a crit servant she's better than Ozy and Rider Altria Altria, but I'm not sure about her since I haven't seen much gameplay...
For future archers if 5 star is you preference then there's Archer of Shinjuku, James Moriarty or something having a 50% NP charge, Nice charisma buff and ignore invincibility, for four stars there's Fujino and Inferno (Tomoe).
If I didn't mention others just wait for other people to respond since I don't completely remember the JP sched and servants.

Most of the other top tier ST servants are already in the game though (Okita, Saberlot, Archuria, TamaLancer, Ozy, Xanzang, Jack, Cu Alter). Anyways, on the type of my head:
Sabers: Musashi, Sigurd, Yagyuu Munenori
Lancers: Enkidu, Raikou Summer
Archers: Moriarty, Chloe, Tomoe
Riders: Quetz, Ridertoki (if you haven't got him yet)
Casters: Illya, Sheba
Assassins: King Hassan
Berserkers: MHXA, Hijikata
Extra: Jalter (again, if you don't have her), Melt, Abigail

Kuro will be a welfare and is arguably the best 4* Archer in the game.
Quetzalcoatl is a great 5* Rider with a high attack stat.
Musashi is a very strong 5* Saber with a buster oriented deck.
Fujino is a good 4* Archer with a good damage buff.