Funny thing about the hype cycle in high tech, things rarely turn out the way cheerleaders proclaim it will. Mainframes did not magically disappear in any of the waves that predicted their demise. The reason is simple – there is a lot of code running on mainframes that works, and has worked well for a long time, rewriting all of that code would be a monumental undertaking that, even today, twenty years after the first predictions of its demise, many organizations – particularly in financials – are not undertaking.
Don’t get me wrong: There are a variety of reasons why mainframes in their current incarnation are doomed to a small vertical market at best in the very very long run, but the cost of recreating systems just to remove mainframes is going to continue to hold them in a lot of datacenters in the near future.
But they do need to be able to communicate with newer systems if they’re going to hang around, and the last five years or so have seen a whole lot of projects to make them play more friendly with the distributed datacenter.