Basically, should we hoard them until all three planned 5*'s are out? Or when a new one is released, will the old tokens still be classified in such a way that they can only contain the heroes who were available at the time they were obtained?
I’m fairly certain that Legendary Tokens, like Heroics, are evergreen.
They won’t “feature” different heroes, but will be limited to 4* (no devil dino) and 5* covers only.
When they first launch, it’ll be a 95:5 % split, so that’s a 5% draw rate for Silver Surfer (~1.6667% for a specific colour) and 5.9375% for any given 4* (except Devil Dino, who is not included) (~1.9792% for a specific colour).
The next 5*'s are due to be released in October and November. In October the draw rate for 5*'s will jump to 10%; both character will have a 5% chance each. It’s likely that we’ll have had two additional 4*'s in that time which will bring them to a 5% draw rate as well. By the time the third 5* is released in November, there will likely have been another two more 4*'s released as well. 5*'s get bumped to ~3.3334% each, while 4*'s have 4.5% each.
Because the lack of option to buy those tokens my guess is that they will look like a stockpiled token from an event, with just the tokens you have sitting there in the middle.