I'd guess that all the flights they were going to cancel in March would have been chopped already. You may want to check in checkmytrip to make sure that the flight is still confirmed (I found out about my cancellation from FT rather than from BMI ).

In my case, I called up and requested to fly back a couple of days later - but that's because it suited me. Otherwise, you may be right - or they'll perhaps offer you a re-route using UA.