Prior to this ruling (ignoring the shake downs by trolls) an individual or small company had a chance of winning a patent case against much larger entities (motions and legal wrangling aside) as the process of discovery forces the defendant to show their cards and prove they aren't infringing with no upfront cost to the plaintiff.
With this ruling, if you come up with the next great search algorithm (software patent absurdity aside) and Bing/Google/Yahoo steals it you now have to foot the bill for the discovery. Without the court order you also aren't going to get very far in that process as they aren't exactly going to welcome you into their office, sit you down at a console, and give you access to their code.
If a company files a motion against you to for a declaratory judgement that it is not violating your patents, that motion would only be able to cover the material that it disclosed to the court. A judgement could never cover anything that they refused to disclose to the court.
You can't get a court to rule that something it has no knowledge of was legal. It has no jurisdiction to make such a ruling.
The burden of proving they infringe may rest on you, but only in terms of the subject material they are trying to get a declaratory ruling about. Perhaps a specific device or product or component. Presumably you would understand your own technology enough to be able to find the infringement or else be able to make a request for disclosure for whatever document you need to show it was infringing. And there is no principle that says that an adverse party requesting disclosure from the other side must pay costs.
I am not a lawyer, but any sane judge would refuse to make rulings about facts not in evidence before the court.