Just had the same news on my 2015 Allroad 272 3.0 TDI with 40K on the clock. It went in for a service last week and Audi inform me that the chain and tensioner need to be replaced, it's a 30 hour job with the engine out apparently, so thankfully it's under warranty, no quibbling on fixing it though. I'm told it's subject to a 'dealer bulletin' but obviously there hasn't been a recall, so assuming it's a bad batch of components rather than every car? At 4-5K to fix it, I'm just glad I'm not paying!