Northern are saying on their website that PDFs of the new timetables will be on their site on 7 May and printed versions in stations by 1 June. In the meantime they are advising customers to consult NRE, but of course NRE will only show the results of individual journey searches, not an overall timetable.
The reasons for the delays in confirming the timetable changes have been well documented but it's hard to see why it is taking them until 7 May to have versions on their website. I presume what will go up then are pdfs of the versions being printed. Surely if need be it would be better to get versions up without the design elements in the pdfs so as to at least get information available?
As for the printed versions only being available on stations on 1 June, two weeks after the timetable changes, where in this day and age does it take over a month to get printing done? That sounds the kind of print lead-in times from over 30 years ago (The fact that the pdfs won't be ready until 7 May suggests that they won't be going for printing until after then. Again, this sounds a very long lead-in time for what is basic design work).