The TPE franchise agreement TSR, from December 2017, was Manchester - Bolton - Preston (no requirement to stop at Chorley), with Bolton replacing the previous Wigan North Western stop. Due to the electrification delay, the change was initially postponed to May 2018, then the further delay caused the current, bodged, timetable, with no stops between Piccadilly and Preston. In May 2019 Northern is planning to introduce the post-electrification timetable on the Bolton line, as originally developed for May 2018. But it seems TPE will maintain the current timetable for the Scottish services, at least until December 2019.
I believe this is all still subject to final Network Rail approval at this stage in the development of the May timetable.