The reason for stating an intent to buy the 737 Max is probably similar to the reason IAG bought the A350 and that is to keep the alternate supplier honest.
Fleet logistics would generate substantial savings by having an all Boeing long haul fleet.....but only if you can buy them at a sensible price. The same applies in short haul, and with the current difficulties Boeing are having with the MAX I rather suspect the price of shorthaul Airbusses are as high as they have ever been, not to mention them likely ramping up support costs.
Conversely the Max price may well be at an all time low and lets face it they won't get delivered/payed for if the problem does not get fixed.