I view Trump's win in PA as a bit of a fluke, along the lines of Carter carrying AL and MS in 1976. It's not going to happen under normal circumstances. The Democrats have to make PA their top priority, however, along with FL.
His win in Michigan was a fluke by historical standards, but his win in PA certainly was not. The state has trended towards the GOP with time, especially with the burbs remaining competitive, while western PA (with the exception of Pittsburg) having flipped to the Republicans. Romney lost the PV in 2012 by 4 points, but lost PA by about the same margin as Bush back in 2000 (the PV was within half a point that time). So yes, I think Trump could've won PA with Sanders on the ticket, but even if he didn't, the map would probably look far different than it does now (with Trump doing a lot better in the south).