Well, while as I've said before superheroes are totally not my thing, I'd consider several factors.
First, is it something your parents actually could! get you if they wanted?
My parents for instance don't do online shopping, so I tend to know if something is available online only it can be something I can buy, ditto with most tech orientated presents.
If it is indeed something your parents could! buy, do they know precisely what you want? While crimbo surprises are rather nice, my brother had a tendency of throwing a few too many strops as a child when he got bought not quite exactly the right thing, or even the right thing but in the wrong box, if it is something specific my parents have had a tendency to just come out and ask, depending upon your relationship with your parents if this is something which is likely to be available for a limited time only, then asking might be a good idea, though by the same token if its soemthing which is likely to be just as available after christmas you might be okay waiting as Jaybird said.
With our dreaming and singing, Ceaseless and sorrowless we! The glory about us clinging Of the glorious futures we see,
Our souls with high music ringing; O men! It must ever be
That we dwell in our dreaming and singing, A little apart from ye. (Arthur O'Shaughnessy 1873.)