The source for this isn't the most reliable, however a TFL consultation is due to be posted soon, I wouldn't get your hopes up too much until that happens.
There is now a proposal for route 154 to be split at Wallington. One route will run from Croydon to Wallington whilst the other from Wallington to Morden. One will retain the original number and the other will receive a new one. There will be increased frequency for the route between Croydon and Wallington. Both routes will still be operated by Go-Ahead London. Passengers heading from Croydon all the way to Morden will be required to change at Wallington, however TfL says this will not affect many. These are short term fixes with a permanent one due to be decided on by March '25 by Tfl and GoAhead London.