They teased a gold and silver RabbitDragon form ages ago

Build BatEngine form

If you pair anything with the Rider Evolbottle it activates a finisher instead of a form, though, barring any possible undiscovered ones that activate a form like Rabbit, Cobra, and Dragon do (Tank is one).

Judging by Mad Rogue, a new Rider using any Best Match is very possible, though.

I would be happy for GoldScorpion to make a show for the first time.

But what I'd hope for is a rider with a device similar to Cross-Z's. Just to match up.

I'd imagine someone who fought alongside Evolto for Mars' destruction.

Which has no merch and could just be Rabbit + Dragon in the Build Driver creating a new form just 'cuz.

EvolTank
https://www.youtube.com/watch?v=BKjLOZqyFro
EvolLock
https://www.youtube.com/watch?v=3PbaWRLHteY

Interesting. I doubt they'll actually be used though.

I believe the FullBottle Buster has a spare sound which some people theorize is for movie merch

Thanks Bladefang for bringing this up in the Build Toy thread
https://www.youtube.com/watch?v=QiYCDHD252U
Guess we have our 3 astronaut Prime Minister characters as the villains and F1Saurus as merch for the movje

So far, we have:
EvolCobra
EvolDragon
EvolRabbit
EvolBlackHole
and now, we have
EvolKey
EvolTank
and EvolZaurus

I think that F1Zaurus is actually going to be a moivie form. Think about it, Zio sounds like Geo. Geology. We usually have two motifs in a rider. Geology is the study of Jewels. Keeping this in mind, I think ZI-O will be a Dino themed rider. We haven't had a dino rider yet. Jurassic World is coming out in July. Like Tenkatoitsu and Drive Arms, this could be a a movie form.

ScorpionGold and F1 don't have EvolDriver sounds. Safe to say those bottles are effectively scrapped alongside the Five Ring (If that was real, can't remember if it was ever clarified it was an actual sound), All Dragon Lockseed and DaVinci Damashii suit