That ended his job, not his career. He's been relatively politically active since then, being one of the top contenders for the presidential nomination from the exact same party despite other scandals of a sexual and moral nature. Definitely not a career-ender, apparently.
At no point has Gingrich ever been a contender in any Presidential race. Getting on TV doesn't make you a contender. Even Herman Cain managed to do that.
There is a non-zero chance Gingrich gets a substantial appointment.
There is a non-zero chance you get a substantial appointment.
Okay, then, the almost $500k/yr he was making a year in speeches and his active involvement and relative success in politically oriented consultancies. Take your pick. He's still being pretty damn successful in political spaces.
edit: ha - misspoke, it was actually almost $5M / year
Hate to break it to you, but Gingrich is near the top of Trump's short list for Secretary of State: