.....While it is likely that the cancellation is part and parcel of a larger drift from a print-oriented publishing model, that can't be certain. As with most of these notices, there was no explanation of the reasoning behind it. Anticipating what is or isn't profitable (or even commercially practical) is ultimately a matter of educated guessing for publishers. When you publish that many titles regularly you have a small number of people juggling a large number of variables. However, if there were concerns that a larger list price might kill potential sales then there may be plans to split the remainder of the run into two smaller arcs and then supplement each with short stories otherwise unlikely to be collected (such as the retro stories discussed on this blog in May and June, prefixed DP09-AP). This might make the earlier half with the Kryptonian tie-in more palatable to Superman fans not otherwise interested in the Doom Patrol, likewise for Secret Six fans with the second half.
.....Well, summer's over. Back to work.