First it should be noted that the chances of a "classic" game, like Bridge, Chess, ect... going through a rules changes is roughly based on age and complexity. So we would expect a "new classic" game to go through ma-ny rules changes over a relatively short period of time. From reading the history of Bridge, it seemed like there was a whole genre of trick taking games. Games like Whist are listed as precursor games to Bridge.

Bridge is a fairly stable product of over a hundred years of game rules iterations. To compare MU or Magic to Bridge is somewhat pointless. It would be much better to comepare MU to one of the precursor games like Whist.

It should be noted that most popular new gaming systems tend to create whole genres of games. CCGs, RPGs, we even see this with board and card games. It is easy to find many examples. The companies who sell these games like their systems to be open ended and some genres like RPGs must stay open ended. But there is no reason the MTG or some variant system couldn't produce a product like Bridge (given 100 years). Imagine an Unlimited set of 100 different cards that are so subtle and well thoughtout in their design that there is no reason to add more cards to the set. Add to that a thoroughly well thought out set of rules that go with those cards. Maybe in another 95 years I might see something like that.

Actually another example of this is SFB. After 20 years, the designers of this game are finding the desire for more new races, rules and ships is decreasing. While the desire to perfect the races and rules they already have is increasing. A subset of the rules and ships, the tourneyment rules, is being played more and more. This could be what WoTC finds 15 years down the road.