On the one hand, such a declaration changes nothing. Section 4 of the BORA is very clear that the courts can not effectively repeal laws in this way. But OTOH, it serves a valuable purpose in providing vindication to the plaintiffs while formally notifying Parliament that it has failed to do its job properly.
The full decision is here. It's interesting reading, both for its long analysis of the court's power to declare inconsistency, and for its takedown of the Speaker of the House's assertion that it violates Parliamentary Privilege. It also has formal guidance for future courts on when such declarations should be issued. I don't think we'll see a flood of such declarations, because in most cases BORA issues are resolved by the ordinary processes of analysis for justified limitations or interpretation to ensure consistency with the BORA. They will happen only in extreme cases. But this is an extreme case, where Parliament essentially ignored its obligation to guard our rights. As the Court notes:
[B]ecause it underpins equality and sustains consent to government, the right to vote is a core prerogative of citizenship in a free and democratic society. The undiscriminating limitation imposed by the 2010 Act on so central a right demanded justification. None was forthcoming.
In a case where Parliament has so manifestly failed, and has overriden protected rights for apparently no good reason, it is entirely appropriate for the Courts to say so. As with other judicial reminders that the law is an arse, hopefully Parliament will now pay attention and change the law appropriately.