"Post-processing"? That's kind of a broad subject, it really depends what you want to do and what features you need. Maybe you could be more specific and what post-processing you are doing.
The Adobe software which you can use for "post-processing" are Photoshop Elements, Photoshop and Lightroom. All come with 30-day free trials. Rather than some stranger across the internet tell you what you need, you would be much better off trying these softwares for 30 days and deciding for yourself which one meets your needs.
By the way, it is my understanding that if you have Aperture on your computer, then it is NOT going away as long as you have that computer.