Well to be fair every game is repetitive to some extent. What games do you like?
-sim racing? you are driving around a town or track over and over again
-open world game? you are going from point A to B completing quests over and over again
-hack and slash games? guess whats repetitive there :P
It comes down to if you like the key aspect you have to rinse/repeat, to know if you like the game. Watch Dogs is no different than any other game in that regard. However if you have little interest in the hacking mechanics/idea....then yea, it could be dull. Just like AC4, if you don't like naval battles or ships...you are going to have a bad time.
To Watch Dogs defense however, I read that there was over 60 different hacks you had control over. That could be PR fluff though, so we won't know till the game is out.
I agree, a game is a game pretty much. What do you really expect? It's the small details that make the difference and Watch Dogs sounds like it will have these. And from a subjective standpoint, it's how you enjoy the theme of the game. Like urban, underground, and tech? Watch Dogs is your game.