At the club's AGM on Monday, Milne revealed a site had been earmarked for new training facilities but said plans elsewhere to integrate an academy on the south side of the city into the overall development of building a new stadium at Loirston Loch has delayed the process.
The Dons have been keen to move from Pittodrie for a number of years as they are unable to re-develop the stadium any further.
Milne told RedWeb: "All the different elements within the masterplan have to be revised so that for example there is a transport strategy that works for the stadium, works for the school, works for the new settlement that takes place, as well as the new Cove Rangers stadium.
"All of that work is quietly going on in the background, but it does mean that the time period is getting extended.
"By the time everything is planned out at Loirston, it is going to be well into next year and maybe slightly beyond. Raising the funds in the current environment could be quite challenging, but we would like to think we could be in a new stadium for the start of season 2019/2020."
Aberdeen were able to wipe out their debts of around £15m in 2014, which Milne said would allow them to pursue their plans to move from Pittodrie and set up brand new training facilities.
Source: Sky Sports