Why should I specialize? Why should you specialize?

Was asked over a company coffee thing.
"Oh you are interested in WPF"
"What are you planning to do with it?"
"What is your next step?"

I was caught unprepared.  I've always seen myself as expert in anything I want to do.  Why not?  Why limit yourself to one technology tree?  What happens when that technology is a dead-end?
I've done Java, and now I'm sold on .NET.
I've done both Windows Forms and Web Forms.
I've done SQL Server 2000, 2008...
Part of the reason I've never been convinced of SharePoint.  Initially it was this portal system.  Then it seemed to compete with ASP.NET 2.0.  After a while... it got bundled into everything: Microsoft Office SharePoint.
Perhaps there is someone really high up in Microsoft that refuses to let it die.

There always seem to be these people (Evangelists) that seemed to know everything there is to know, about everything.
How do you go about becoming one of those?

Anyway, I can see the company's point of view.  Master of One Trade is easier to sell (and train) than Jack of All Trades.

But I still feel if I had to abandon any one of my many interests, it'd be like cutting my arm off :-(