日程 and 予定: a day-by-day schedule and a planned activity
Separate changes to a trip's detailed schedule from the plan to travel, reading undecided dates alongside an existing travel plan.
Activities arranged by date and time
日程, read にってい, means a schedule of activities organized by date and time. 旅行の日程を一日ずつ確認しました。 says that the trip schedule was checked day by day.
初日は移動、二日目は見学という日程です。 describes travel on the first day and a visit on the second. Separate the activity assigned to each day.
A planned or expected activity
予定, read よてい, means a planned or expected activity. 午後は美術館に行く予定です。 says that a museum visit is planned for the afternoon.
来週の予定を教えてください。 asks for next week's plans or schedule. 予定 is not limited to a fully completed detailed timetable.
The detailed schedule and the overall plan
日程はまだ未定ですが、旅行に行く予定です。 says that the detailed schedule is still undecided, but there is a plan to travel. Separate the activities on particular dates from the travel plan itself.
日程を変更しましたが、旅行に行く予定は変わりません。 says that the schedule changed, but the plan to travel did not. Do not expand a detail change into canceling the trip.
Does 日程はまだ未定ですが、旅行に行く予定です。 mean there is no plan to travel?
Show the answer and why
No. There is a plan to travel, while the detailed day-by-day schedule has not yet been decided.