According to NYCC's official website
, yes, Mattel will be there.
The NYCC will be held on April 18-20th.
(Interesting. Hasbro isn't listed as one of the exhibitor's. Maybe they haven't bought their space yet.)
Traditionally Hasbro has only gone to SDCC and line-specific cons like the GI Joe con, Botcon and the Star Wars Celebrations. You would think that having the Marvel license would get them to more shows...