" SaaS and open source eliminate the second component of this lock-in, but nothing can fix the first part."
Is that true?
Drupalgardens.com is a SaaS for very simple websites but doesn't have data lock-in as you can export your site, code, configuration, content and all and host it on your own set up if you need to. Even business logic stored in the way your site works can be exported.
Now... Drupalgardens is obviously a very basic example and high end enterprise systems are unlikely to go the way of drupalgardens + Drupal. But I dunno if its true that "nothing can fix the first part". If Salesforce were to opensource their whole thing and allow you to run salesforce on your own servers you could essentially get to a point where you could migrate a salesforce site between vendors or host it yourself.