Judging by the facebook posts and comments in various British newspapers regarding Wiggins' omission from the TdF squad, and the fact that Froome only managed 5th in the BBC SPOTY despite both Cav and Wiggins winning it the previous years, suggests that protecting Froome isn't going to protect that cycling boom as you put it. If they were being populist, Wiggins would be riding for the TdF, not Froome.
That said a complimentary argument to that would be that Sky really need Wiggins to win the TdF because winning may silence a lot of the criticism. But British fans aren't stupid: the contents of the book, the TUE and the weak management at Sky not being able to harness Wiggins and Froome together has been noted, and the fact that Sky aren't doing what is expected of them to nurture British talent as a supposed quasi-national works team. 5 British riders out of 28 GT riders that Sky sent last year were British. So far this year it will be three when the TdF starts. The knives are slowly starting to sharpen, success may delay that for a while longer, but I'm surprised the Daily Mail hasn't called Froome a plastic Brit yet. They probably will when he starts losing.