I don't think Wlad will jump on Haye because that would be a huge mistake. Haye is a fast, crisp powerful counterpuncher so rushing at him would only bring harm to Wlad. Klitschko's best bet would be what he does best, and that is to stay behind his jab and keep his distance.
I really don't think it will be early or mid rounds. If Klitschko knock Haye out, it will be late as he will take his time and stay cautious trying to avoid being countered. Haye is very much a live underdog who I am not counting out at all. I have actually changed picks a few times.