Already, some plans for springtime on Broadway that looked firm a week ago have changed. Key among them was the decision by producer Robert Whitehead to have Terrence McNally’s “Master Class” add two more try out runs – at the Mark Taper Forum in Los Angeles and the Kennedy Center in Washington – before bringing the show in. So “Master Class” won’t arrive until the fall, when Whitehead hopes to put it in the John Golden Theater, currently occupied by Jackie Mason (don’t even ask about his performance schedule). At any rate, that freed up the Ambassador, which just may be where “My Thing of Love” will land, if producers Barry and Fran Weissler can finish raising the money for their Broadway Alliance production. Or the play may still end up in the Nederlander. Stay tuned.