An interesting interview with an IBM guy on the role of the mainframe in business and the latest buzz on cloud computing. He has a lot of good points and most importantly his points are based in reality and not academic discussions. To summarize, the mainframe is still the key system in a lot of companies, this is especially true in financial companies (I can attest to that). The idea that these companies would move these systems off the mainframe and into some cloud of services located anywhere and hosted by anyone is completely ridiculous. That will be about the same adoption rate as companies moving to a successful SOA. :)
Some of his points are also not valid as well. Running programs in complete isolation is certainly possible on the mainframe but only if you have architected and setup it up that way. I've seen regions bring down regions because of some shared piece of hardware or pipes. As with anything the touted benefits are available if you actually know what you are doing.
I ultimately believe the mainframe will die a slow death as a couple of generations start leaving the workplace. The lack of skilled resources in that field has already started to have an impact. That being said it's replacement will probably not be the cloud. In the meantime it's alive and kicking so brush up on your green screen.