He won't be booted over one duff mark, but he might be encouraged to be a bit more objective in his marking, rather than basing it too much on what he personally likes, or what personally bores him. That's what it felt like he did when he marked Jorgie down, or when he undermarked Sebastien earlier in the series.
The reason he's at risk is that being a "dance expert" is not particularly unique. There are thousands of them in the UK with just as much experience and dance qualifications as him. His edge was that he'd already been on tv and had a tabloid profile. If they don't care about getting another celeb on the panel, he would be very easy to replace.
I have found Louie fairly annoying, but he's had good weeks and bad weeks. Just as I think he's doing well, he does and says something stupid, or makes it all about himself. If he is back next year, I hope he learns a bit more about skating, or takes advice from the skating experts as to how difficult a routine is before marking a person down for being "boring". I'm not saying he's to mark the skating, but he can't just pretend the contestant isn't doing that. At least Jason always seemed to take that into account, but he could skate and knew enough about it to respect that side of things, even if he wasn't marking it.
The most annoying thing about Louie is that he acts as if Robin and Katarina don't know anything about performance, and that he's representing the views of the general public.