Many people are either planning to, or are in the process of moving to open-source and/or cloud-based solutions in order to reduce costs and reliance on local IT resources.
The problem is that whilst the destination maybe clear the journey still has to be carefully planned!
If you currently run a complex set of applications and have data on a pSeries or iSeries environment you cannot simply copy everything into the cloud, or onto a Linux server and expect it to work out of the box.
You first need to measure your current system(s) performance and create a map of all the data you hold, and how it flows in and out of your organisation, and then ensure that your new systems can provide a suitable replacement. You also need to plan for a period of parallel-running and testing, and maintain your legacy system(s) until such a time that you can cut-over. Licencing and compliance can also be massive challenges as you may need more Linux (virtual) servers and local regulations may prohibit or restrict your options.
Fortunately AIX has a lot of tools that can make this migration a lot less difficult! Since version 5.1 AIX has included what IBM calls "Linux Afinity" and this means that you can install many open-source tools such as the GNU compiler, and use that to compile a great number of open-source products such Nagios or wget, and there are also sites that provide ready-made RPMs e.g. Perzl or Bull.
AIX can work with both its native LPP (Licenced Program Product) packages, or the open-source style RPM (Redhat Package Manager) format. IBM also provides a large number of Linux RPMs as part of its Linux Toolkit.
The other great advantage here is that you can measure the performance of an open-source application such as PostgreSQL whilst both on Power and Intel or ARM based systems. You may even find that they perform better on your pSeries server and you actually need more x-based systems, or cloud-capacity to maintain your service level.
Another option is to create Power-Linux partitions on your existing hardware. IBM currently supports both Redhat and Suse distributions and you can also install other versions such as YellowDog Linux which means you could actually run a complete Linux environment without having to ditch your pSeries or iSeries servers.
You should also not overlook the fact that IBM has done a huge amount of work creating hardware and software based solutions such as shared-processor-pooling and active-memory sharing and expansion which, regardless of the OS, can result in huge cost savings.
The other "Elephant in the room" is the IT resource required for both the planning and execution phases of your project as they will need both AIX and Linux/cloud knowledge and be able to work comfortably in both environments.