Looks like Slingshot and Wildrider are definitely limited edition exclusives from Hasbro, as they have appeared in a Diamond/Previews listing for May... suggesting a shared exclusive at American comic shops and ToysRUs America.
(no idea if they will come here, or what other American sources might have them as well)

Since the names being used are Quickslinger and Brake-Neck, it shows that Hasbro America must still be missing the trademark on Slingshot and Wildrider (or recently lost Wildrider, as it was used on the 2010 BotCon set). And it shows that when Hasbro Australia were saying that "Slingshot" and "Wildrider" are not on their release listing, it was technically correct... in that they are not general release toys, and, those Gen1 names would not have shown up on any future product listings - so even if they are coming here in some way, Hasbro Australia wouldn't have known that Quickslinger and Brake-Neck are the current names for those characters.


At least if they do come out in May, and don't get released here, those people going to BotCon in June might have a chance at finding them if somewhere like TRU gets them... or BBTS (who will charge a lot more than retail for them in the Dealer Room like they did for Metroplex in 2013).