Gangplank will be back. But...
It won't be the same Gangplank. It would be someone else who took up his name.
I have the feeling that 'Gangplank' isn't even his name, but his code name that his father Vincent designated to him and made him believe that it's his name all along. In other words, this opens up about chances of someone else taking the legacy of Gangplank, and thus his gameplay and stuffs, without reviving the old Gangplank.
As of looks... well maybe the new Gangplank have been quite stinkin' rich enough to effort a plastic surgery to make him look like GP?