Bobs Worth just keeps finding, and will surely outstay everything in the Gold Cup. Silviniaco Conti commands respect, but - surprised as I am to say it - I think Tidal Bay might be his biggest danger - though he's had a tough race today, and he isn't getting any older.
That apart, Bobs Worth looks nap material in the Gold Cup.
The three you mention are all proper Gold Cup horses. These are the type that should be contesting it. If Long Run were to return to form he is still young enough to make an impression also.
Hopefully connections of Cue Card will be realistic and aim for a follow up in the Ryanair. I'm doubtful he'll place in the Gold Cup.