I am not sure really.
A lot depends on what people think about what this means. Remember, nobody knew that Black Wednesday would happen at this point. If people think the economy is going to pick up, that Major is guaranteed a small majority at the next election - then Kinnock would be pretty much pressganged into staying on to take the hit from that and give the next leader a clean slate.
If people think 'we've got the Tories on the hop', then Kinnock is in greater difficulties. The temptation was always to ditch Kinnock and put Smith in, because that would restore the leadership's relationship with the left and the unions to factory settings and would reap electoral dividends. Consequently, people may find the allure of new leadership irresistable.
Kinnock was depressed and exhausted at various points by the end of his leadership, so he may just chuck the towel in anyway whatever the prevailing advice. Probably you are right and Kinnock would go, but I wouldn't say it's a certainty.