They have every right to keep quiet about what they're working on, there's nothing "wrong" with that – it's just not too smart, in my opinion. They miss a ton of marketing opportunities. A photo here, a snippet there ... just imagine what would be going on in a forum like this if they'd let us witness their progress. Instead, a lot of people will silently lose interest. Not the die-hard fans, of course, but ones who don't necessarily google "Mark Knopfler" twice a day. These people - and they're the majority at every MK concert - will just turn elsewhere, somewhere where they're not being bored to death.
Now, again, passing on obvious marketing opportunities and ignoring how online communities are built and entertained these days is no crime. It's just not very smart if you want to make as much money as possible from your art. And while Mark himself may no longer give a fuck about that, rest assured that his outmoded hangers-on certainly do.