Your going to be changing operating system versions with a newer machine which will unfortunatly require upgrading and installing more recent copies of your software and plug-ins.
If you have a Mac that's running 10.6 or earlier, it's likely using PPC based software that will not run on the newer Mac's with 10.7+ and above. New Mac's are coming with 10.8 and 10.9 is due to be released soon.
So what your going to have to do is research your respective softwares yourself and plan a appropriate upgrade path.
http://roaringapps.com/apps:table
If you have very expensive software and want to get a lot more lifespan out of their respective versions, you may want to consider installing Windows in BootCamp partition on the Mac and using Windows 7 versions of their software as Windows versions are supported a lot longer than OS X versions. Also there is a lot more software selection on that side as well.
The OS X side can be used more online and more risky behaviors like surfing, emailing and transfering files among other machines which is the prime source of malware, also the rapid OS X upgrades are not going to bother you as much as your expensive software will be on the Windows partition and offline mostly (except for updates).
At least on Mac's we have that dual choice option, which is a nice advantage.