Yes, absolutely. In legacy maintenance-only systems. But there are far better alternatives for new development.
For years I've been seening folks come out with these "death of the mainframe" claims, and yet they continue to be wrong. There are applications that neither minicomputers, PeeCees, nor Beowulf clusters of commodity hardware can touch for any amount of money. If you need real 99999+ availability on a box with massive disk bandwidth among other things, you're just not going to get it with anything but systems designed from the ground up to meet the desired requirements.
To even come close to claiming 5-9 reliability on anything but the most expensive minicomputers, you have to be living in a dream world.
Sure, in raw computational horsepower for special types of problems that benefit from hightly parallel computation, a cluster of inexpensive boxes is a fine solution. If you need a system that can massage and manage multi-terabyte databases, a glorified desktop box just won't do the job.
There are valid business uses for all classes of computers, because each fills a specific type of need. (These roles shift and change a bit over time though as the tech advances.) To say otherwise is to display ignorance.
Amen
Another way to say it is that there is a place for a bulldozer and a place for a tractor-trailer rig and a place for a pickup truck and a place for a sedan and a place for a Harley.
But 1,000 Harleys are not better than an 18 wheeler in moving product for Walmart.