Buxton's future performance should be expected to be similar to his past performance, which has been highly affected by injuries. There's no reason to expect him to remain less injury-prone.
He's 27 now - pretty much in the peak performance period for most MLB hitters. Of course, there are exceptions - but as hitters near and age past 30, we typically see slight annual declines. Buxton's injury-tendancy might accelerate his decline.
IF he stays healthy and plays 80-90% of the time, he could be an significant impact player/All Star. And he will definitely make the Twins a better team if he plays that much.
Buxton is an exciting player and, if he's playing regularly, will be a draw for fans. Even if the Twins are mediocre, he will be fun to watch - if he's on the field and in the batter's box.