Actually, the Mets are getting a new stadium, but Shea is only 43 years old, they don't needs a new stadium.
And I agree, I don't want to see Yankee Stadium torn down. I have many fond memories from there, but the place is worn down and outdated. What the city plans to do is build a park around the facade of old Yankee Stadium, tearing down only the rehashed areas of the stadium. So it's not like the whole thing will be destroyed, just the newer portions. They will make the old portions of the stadium into a baseball park for the neighborhood, which is necessary since they are taking over McCooms Dam Park for the new stadium.