About five years ago I reported widespread failures of timing belt pulleys on 1.4 and 1.6 16v petrol engines and VAG changed it. VAG had used plastic idler pulleys, the same as GM used in the 1990s causing a previous catastrophe. Rather than admit this failure to learn the lessons of recent history, VAG issued a blanket 4 year / 40k mile change policy on all timing belts for all models, so the dealers could make a bit of money out of it. Independents reckon and always have reckoned 4 years or 60k miles whichever comes first for the diesel engines. Yes, timing belt failure would cause damage to the TDI.