Eriksen is extremely good at what he does at the moment, particularly in this system for Tottenham where he is not really challenged by anyone else. He is never rested, he is seemingly never injured - it will be interesting next season when they have more matches, more spotlight on them - more of a challenge compared to this season and last. Playing at Tottenham has been secure up until now, a team challenging the better teams without anyone really paying attention or raising their game. I believe that period is over now; Tottenham will not go under the radar next season - they have been too good this year and all teams will raise their game and be aware. It does help him and Tottenham that he has an excellent delivery from set-pieces, something all great teams (any team) would crave. Man Utd does not, a lot of good teams have several people standing over the ball at all times - it does not create stability whatsoever.
I do not think Eriksen will leave Tottenham, he is most likely one of the first to say he is happy where he is. As a Scandinavian he is always going to be humble (in the Ole Gunnar Solskjær-sense) - at the same time he is going to be the one to realize that he is not what Barcelona or Real Madrid needs. Both in terms of playing ability and lack of charisma. Tottenham are lucky like that; they have all these good players but 99% of them lack charisma or selling points outside of what matters the most; footballing ability. The great clubs are always looking for the best players with the most charisma and marketability, something that catches the eye of fans and sponsors.