This is a valid suggestion and would make installation easier for those that are unfortunate enough to have an older Pentium M or a similar crippled CPU. Linux Mint 15 will use Ubuntu 13.04 as a package base, and AFAIK that again like Ubuntu 12.10 comes without support for non-PAE CPUs.
It is a bit more complex that you would imagine perhaps. The kernels on Linux Mint come from the Ubuntu package base. Those kernels are currently not long-term support kernels, and hence are not supported by the kernel developers. It is the Ubuntu kernel team that maintains these kernels. Including a non-PAE kernel on Linux Mint would mean the developers get another task; maintaining the kernel... That probably goes beyond what the team has time for to do, or at least if nothing has been implemented for this yet it is cutting it close as we are close to moment of release.
This issue was raised at the time of Linux Mint 14 as well, and the recommendation currently is to use the LTS release--Linux Mint 13--for non-PAE CPUs.
Fortunately, there are a lot of ways you can install these Linux Mint versions on non-PAE CPUs. Some users have gotten a kernel from somewhere else and included that on their ISO (can't find the post right now, but here are the steps for Ubuntu 12.10: http://www.webupd8.org/2012/11/how-to-i ... n-pae.html
). Other users have installed Linux Mint 13 and then upgraded it in place to Linux Mint 14, retaining their non-PAE kernel. Something similar will surely be possible for Linux Mint 15, if no other option is given.
Of course this is a bit more involved and ideally non-PAE would be supported out-of-the-box. I'm hoping that will have been worked for on Linux Mint 15, but I'm not privy to what will happen for Linux Mint 15.