We don't have any current plans to drop support for Windows XP. Our software should work well on either Windows XP or Vista. When you purchase a license for our products, you are guaranteed one year of free updates and support and I would expect that a year from now we will still be supporting SecureCRT and VShell on Windows XP.
We don't currently offer a version of SecureCRT for use on any UNIX platform, but your decision to move in that direction is up to you. Windows is probably here to stay too