If I was a Spurs fan I'd be a little worried. Some fans talk about continued improvement by keeping the team together but progress is not linear and it's even possible that last season was a peak that is not easily replicated, look at Chelsea's demise from champions to 10th (not that I see this happening to Spurs and of course Mourinho was certainly a key factor in that).
Obviously a major obstacle to Spurs' trajectory is that your main challengers, whether for the title or Top 4, have all strengthened, and most substantially. There may be a case against Chelsea but I doubt it and Arsenal IF they lose Sanchez, but that hasn't happened yet. I voted against Spurs for Top 4 for that reason. You simply can't stand still in football as history proves, even the likes of Ferguson, Paisley and Shankly, at their pomp, would freshen their first teams substantially year on year to sustain the internal competition and keep players hungry and pushing the limits of their abilities.