In recent weeks I have done some wok in SEN type schools where there are 3-TAs for every teacher. It needs to be that way. I do not believe there is any chance of anyone trying to slash the numbers on a large scale in such an environment.
In mainstream schools the numbers have proliferated to deal with all the additional needs that have become more prevalent (ADHD etc, slow processing of information, dyscalculia etc), so it's right to review whether the numbers are justified, but given how inexpensive TAs are compared to teachers (and TAs don't get paid in holidays) and the work they do with small groups, I think as a cost-saving measure the figures wouldn't stand up as we'd need more teachers. Certainly more good teachers would leave the profession.