They may or may not ever get made.

I'll start:
Leader class HM/TM Skorponok.
Voyager class Skyfire.

I'm sure I'll have other ideas.

 

Titan Skorponok only

 

Nautica, Rung, mass-retail Roller, Veloci-- hang on-- (throws issue of MTMTE over) Save some time.

Also Animated Wasp. NEVER GIVE UP

 

A Leader or Voyager Nova Prime.

 

Victory characters (I'll assume Star Saber and Deathsaurus are coming + Greatshot from Takara):

Victory Leo
Blue Bacchus
Galaxy Shuttle
Thunder Arrow (w/robot mode)
(Leo and Bacchus can be voyagers, the other two at Leader class to have Titanmaster compatible base modes)

 

While kind of likely, I'm kind of sceptical that Black Shadow will be slightly retooled into a Leader Class Thunderwing but goddammit I need this to happen. He needs to not only be massive but in scale with PMOP so the two can do battle all over again.
It would also be great to see a Deluxe Class Terrorsaur that has a beast mode.
Also, a Lockdown toy that has more of a G1 aesthetic than Animated and either Bayverse toy.
Hasbro are missing a massive opportunity by not attempting to make a new Armada Sideways for Titans Return.
In fact, can we just have toys of all the meaningful Armada characters but now articulated?

 

Titan class Predaking that's as well made as Devastator.

 

Leader or Voyager class Star Sabre.

 

Deluxe Blue Bacchus to go with Black Shadow (Sky Shadow)
Autobot Spike
Omnibots
Insecticon Venom to go with the Fansproject Deluxe Insecticons OR Barrage/Ransack in Legends scale to go along with Hasbro CW Chop Shop.
Rotorstorm
Rack n' Ruin
Stalker and the rest of the Predators
Raiden
Landcross
Grandus
new BW Terrorsaur
BM Botanica
I've also always wanted a plastic representation of the TORQ III computer from the episode "Day of the Machines" of the G1 cartoon

 

Moonracer and Firestar. Oh, and minivan alt-mode Chromia.
Pretty much all the missing G1 fembots. Animated had couple characters that need to be toy form as well.

 

Titan class Metrotitan
G2 Devastator in yellow and orange
G2 Defensor
The "missing" Animated toys.

 

MP Dinobot, MP Terrosaur for sure!

Leader/Voyager class Nova prime, no stupid HM gimmicks if possible.

An attept on Voyager G1 Dinobots. I got the Planet X ones but you know, official ones could be more geewun-ish.

 

RID:
Optimus prime
Sideburn
Prowl
Xbrawn
Bullet Train Team

Beast Was:
Lio Convoy

 

Signal Lancer please.

 

Ark and Decepticon base parts such as computer stations and medic bays to use in dios

 

Came to say exactly this.

 

Leader class Skyfire, get over the Macross nonsense allready Hasbro and give us the guy from the cartoon.
Deluxe Paradron Medic as an online exclusive NOT a club excusive + MP Paradron Medic
Leader class Onyx Prime and a Lord Imperious Delirious retool.
Voyager tapedeck Soundwave.
Voyager Cybertronian tank Megatron
Titan class Overlord (with a good citymode) and Tidal Wave (with a citymode)
Stalker and the rest of the Predators
Insecticon Venom to go with the Fansproject Deluxe Insecticons
A non titan Devastator and Predaking
Deluxe Quintessons.
deluxe or voyager Allicons and Deluxe Sharkticons
MP Beast Megatron.
MP Barrage
MP Mindwipe
MP Galvatron
MP Astrotrain
MP Thundertron
Voyager Shockwave
Legend class Reflectors
Deluxe class Deluxe Insecticons
Voyager class original Headmasters
Leader class and Titan class Scorponok
Voyager class transformable Pretender shells and Legend class transformable inner robots:
PRETENDERS!
Voyager Apeface and Snapdragon
Junior Headmasters
Leader class Doubledealer
deluxe class TR Misfire, Slugslinger, Crosshairs, Sureshot, Pointblank and maybe Cyclonus
deluxe class double targetmasters
the original G2 characters particularly the Rotorforce, Dreadwing and Smokescreen, the Laser rods and the color changers

 

MP Triggerhappy