It is unlikely, but you could just send them an email and ask. While the big 4 typically open up applications for training 3 years in advance (e.g. training in 2021 would open in Aug 2018) and these spots fill up quickly, spots do open up here and there because of business needs or someone leaves. I myself secured a training contract for 2021 at a big 4 firm despite it being way after application season because one of their trainees left to do his masters.

So, my response to your question is that no one here is likely to know, but you could just ask them directly. They are usually forthcoming with a reply.