As far as I'm aware, the latest and last version of Aperture is 3.5.1.
Apple has said it will continue to support both iPhoto & Aperture (in their latest versions) with Yosemite. For how long we don't know, but at least until mid 2015. Thereafter, my reading suggests, Aperture will still be usable as a stand-alone (just not supported) and it will be merge-able, along with iPhoto, into Photo.
My point is: is it worth the expense of getting Photoshop Elements and then finding a way of recovering your Aperture images — versus the modest cost of updating Aperture (if there is a cost) and then sticking with Aperture until either you merge it with the new Photo, keep it as a stand-alone or then consider Photoshop Elements or better still, Lightroom?