They'd be worse off?

Blackberry has two problems right now, they don't have any apps so nobody wants to buy their phones, and they don't have any market share so nobody wants to make apps for their phones.

And yet.

In terms of both market share and app availability, they're better off than Sailfish, or FirefoxOS, or Ubuntu Phone or Tizen. In fact, it probably has more users and more apps than all four of them combined. Switching from their current OS to any of the other alternatives in the marketplace besides Android or maybe Windows Phone is a step BACK for Blackberry, not forward.

Using a niche operating system is their problem.

Exactly. The industry can't sustain multiple operating systems unless there is some way of abstracting the development platforms. Solutions do exist for this but they are generally very poor quality and force a lowest common denominator approach.

This is a smart and very overdue decision by Blackberry.

+1 for Sailfish.