You never know, this year the Daylight Saving Time switch might work out differently -- but why take the chance? Over the years, Apple's iOS platform has run into a few hurdles when it comes to handling the semiannual clock shift forwards (in springtime) or backwards an hour (in the autumn). From wakeup alarms that triggered an hour early or late, to ones that simply never went off at all... you get the drift.
The most recent hiccup for iPhone and iPad users with Daylight Saving Time handling was merely cosmetic, with the Calendar app misidentifying the correct time back in October of 2013. That was nothing compared to the Great Late Date of 2010, where people missed appointments or were late for work due to wonky alarm triggers.
To be clear, we've yet to see any signs of similar problems for the iPhone with the switch this year, which triggers at 2 AM local time tomorrow (Sunday) morning in most of the United States. Nevertheless, prudence and painful experience suggests that a backup alarm clock (or using the timer function of the clock app, to count down the actual number of hours you need to sleep) may be a good plan for Sunday and Monday morning. If you want an app that can wake you selectively at the "right" part of your sleep pattern, I personally use and recommend Northcube AB's $0.99 Sleep Cycle app.