The plan for a long life span is always good, but let's see how it sells first.

It will not have the player base to justify support over 5-10 years.

Well considering Fable III sold over 5m it wouldnt be doubtful if it did.   

If Lionhead can create multiplayer that is worth going back to then I don't see why not.

You do realize that if they do keep supporting the game with free content for 5-10 years then they are going to be putting a lot of money into the project. So they will need a lot of sales in order for such a model to work. And if the dlc/updates cost money they are potentially alienating a part of their player base.

Ofcourse it all depends on the budget of the game as well as it's scale, but constantly supporting a game with new features for 5-10 years is very expensive especially if the game brings no revenue other then the initial game sales. 

And you realize that Fable is popular and that Fable Legends is focused on multiplayer(Much like an MMO).  

Will it be successful?  I really don't know, but Fable has a better chance of making it successful than most franchises.

As for alienating the game, some MMO's are paid monthly.  DLC won't be too far off from that even if a fraction of the people buy it. 

Nice to hear. I like the idea of an online mmo type fable. Ive always thought the game would suit that. Loom forward to the beta.

Ugh its an online game?  There goes all my interest in this game.

Honest to god fable legends has a better chance of being better received if it borrows alot of ideas from kingdoms of amalur reckoning and the witcher plus this sounds like an MMO which brought down my hopes.