I don't think so. Dann has taken to the Premier League like a duck to water and I doubt we'd sell him for anything under £8/9m at this point. He's one of the best English cb's around which is why Hodgson has been watching him so closely. He's proven himself to be top Premier League quality, while Dunk could go either way.
But Dann "could have gone either way" which is why he went for £3m to Crystal Palace and not big money to a big club.
No one is speaking to Dunk until they put £5m on the table, so it's unlikely to be an imminent issue for us, even with 7-10 Premier League clubs sniffing around currently.