In think you are right with your observations.  Tight budgeting and economic downturns around the globe are making research expenditures to be squeezed.  But generally, I do not think the essence of sabbatical leave has outlived its purpose. Just as the economies fluctuates and picks up over time,  so also will more openings avail themselves and normality will return.  Just my thinking.

It is meant to be  a learning curve whereby both the lecturer on leave and the hosting institution share their experiences and learn from each other. During the period both parties are expected to carry-out projects whose outcome can be global ground-breaking news/ solution to major problems etc, lecture/tutor/mentor, supervise research students in areas of specialisation, attend meetings/conferences/workshops and explore ground-breaking research work together for local, national and international benefits. Learn how to utilize facilities not available at your institution so that you bring back that knowledge for your institutional growth. It may further create opportunities for exchange programmes, sign MOUs/ MOAs and even create opportunities as visiting lecturers/ professors from other departments. You return back to your station with new brilliant ideas and new academia relationships.

Sabbatical leave has not outlived its purposes but the global economic meltdown possess a great bottleneck in securing one. It is becoming abysmally difficult nowadays to be granted one; there is therefore an urgent need to resuscitate this laudable academic culture. How I wish there would be an academic forum to thrash out this matter before the extinction of this capacity and intellectual development  academic programme.