Bale has admitted that he thinks Ronaldo is the best player.. he clearly looks up to him, tries to imitate him and has shown interest already in starting his own brand and becoming somewhat of an icon.
Would simply being in the Champions League be enough for him Glaston? Plenty of players have left teams who constantly compete in the Champions League because they want to challenge for titles and have a good chance at winning the league.
Bale seems ambitious from the interviews we've seen. He may enjoy being part of this project, hoping to get Champions League football to White Hart Lane - enjoying that he is the big fish, enjoying the praise and awards - but how long will that satisfy him?
If he wants to imitate Ronaldo and be up there considered as one of the best in the world - would he really stay at Spurs?
If he wants to become a global icon and have a following and be marketed - would he stay at Spurs?
Generally, the players considered the best play for the best teams. The players who are most marketable play for the best team.
Maybe he could be the exception.. But I doubt it - I'm sure he could do well staying at Spurs, but I think he has ambitions higher than that.
I definitely believe it's a question of 'when?' and not 'if'.