When considering what will be the oldest version of any operating system we can effectively support, there are two considerations: the number of users of that version and the cost for us to support it. When the number of users is small but the cost is large, obviously it probably doesn't make sense to support it. This is the case we have run into with OS X 10.5.
Looking at the numbers, OS X users essentially fall into two camps: those using 10.5 (Leopard) and below and those using 10.6 (Snow Leopard) and above. According to the data we have gathered, over 80% of OS X users are using 10.6 or 10.7. While that does mean that almost 20% of OS X users are still using Leopard or earlier, that number is dropping.
Next, let's look at cost. Because of improvements in 10.6, supporting 10.5 and earlier often doubles the amount of effort for us because we have to code things one way for 10.5 (and earlier) and another way for 10.6 (and later). This means we fix fewer bugs and spend more time and energy on new features than would otherwise be unnecessary. Supporting 10.5 would make it impossible for us to use some of the new features of OS X 10.7 (Lion) as well. So the cost of 10.5 support is pretty high.
Because of these two factors, we have decided that the minimum OS X version we will support for Cocoa starting with Real Studio 2012 release 1 will be OS X 10.6 (Snow Leopard). Because Real Studio 2012 Release 1 will also be a Cocoa application, the minimum version to run the IDE will also be 10.6.
If you need to support users with 10.5 and earlier, you can continue to compile a Carbon version for those users. Projects saved in 2012 R1 will open in 2011 R3 which means you could even compile for Carbon on PowerPC if necessary. However, in this case, do NOT save your project in 2011 R3 once you have saved it in 2012 R1 as you may lose data. Just use 2011 R3 for compiling to PowerPC.
We don't make decisions like this easily or lightly. But they must be made in order for Real Studio to continue to move forward.