Disney can raise their prices at anytime and there is no warning. There was a price increase earlier this year and its possible there might be one more but who knows.
Recent increases have occurred in February on an annual basis.
As others have said, don't expect any warning. If you have travel plans beyond January 2020 it would be a safe bet that you should lock in your prices now, if it's a concern.
Right now it's $139 for Peak, and $159 for Holiday. I really can't see them raising that now.
If those tickets aren't raised then it will be hard to raise the lower cost tickets because there won't be enough difference between Value and Peak to spread the crowds.