It depends. Form in rugby seems to ebb and flow. (Remember that the pre-WC warm-up matches were so close. Wales and Ireland have improved in the short amount of time since then, and I see no reason why England can't.) There are some simple solutions to big problems in the England squad at the minute (MJ would only have to change a few selections, and I think we'd see a much better England), and some players could easily take off in this tournament for England yet. Lawes, Croft, Youngs, Foden, Ashton are nowhere near their potential and some of our better players such as Palmer and Flood are being kept on the bench.
I mean, at this minute you'd put money on Wales/Ireland, but don't get ahead of yourself
On the other hand, the idea of England, as bad as they've been in the breakdown recently, coming up against an on-fire Warburton is a scary thought...