Remember that Aperture creates "Libraries" to store your "Projects" - when you create a new Library with new Projects, you are given the option to specify how the files you import into your new Project are referenced. Specifically, do you keep your imported files in their location and just reference those files in the project, or do you import your new files into the Aperture library for the Project.
My point is, when you are backing up your Aperture application, make sure you also back up your Aperture libraries, especially if you import your files into the libraries you have created. Aperture works in Yosemite, and Apple's raw support is built in to the OS (not Aperture) but I understand your desire to figure out a plan for the future.
Luckily for you, you have choices when it comes to raw converters for Mac. If you are the type of person that needs to organize and keyword and tag and GPS and IPTC all of your image files, then you will also need a strategy for DAM (I use Photo Mechanic when I need to, and I also use XNViewMP [free] but I do not do tagging and key wording, etc.). That aside, there are several raw converters that I would suggest you look at purely for raw conversion quality, which is more important for my needs than DAM.
Iridient Digital just released v3 of its raw converter, Iridient Developer. It is top notch and builds on a long history of high-quality raw conversion. Unlike most third-party raw converters, it supports both ICC and DCP camera profiles (so you can use custom profiles that you have built with practically any profiling software) as well as camera-lens profiles that are part of Adobe Camera Raw. It also has adopted the use of the ACES color space as its internal working space, and offers L*a*b* curves, specialized mono demosaicing for black and white conversion and a specialized sharpening algorithm to accompany multiple levels of conversion quality algorithms. You can link it to pretty much any external editor to make workflow connections a snap and it handles batch jobs with a dedicated batch mode. You also have explicit control over conversion output color space - including no color conversion during output if you need to produce an RGB image for profiling with no color conversion. There is a free trial: http://www.iridientdigital.com
Raw Photo Processor (RPP) is a high-precision raw converter that aims to produce the highest quality conversion with no frills. The application is free, but you can unlock several features with a donation (multi-core processing, built-in camera profiling, workflow helpers). At first the process seems a little quirky but once you get it, you will appreciate the quality of the conversions RPP produces. This application is suited for folks who work with raw conversion as a first step in the image processing chain, and who routinely take their images into photoshop or other pixel editor. This raw converter is superb at what it is intended to do: http://www.raw-photo-processor.com/RPP/Overview.html
Of course there are the other commercial solutions, like DXO and Capture One, as well as open, free solutions like Raw Therapee. They are all very good.
I'm not sure how you work, and how much processing you do on a raw file in Aperture, so some alternatives might be better suited for your workflow than others. For context - I use many different raw converters for many different reasons. I do not prefer Adobe Camera Raw, but it has its place sometimes. I, personally, work with images in Photoshop after raw conversion and I find Lightroom to be redundant to ACR and the LR workflow is a waste of time for me. The local adjustment tools are clumsy and can slow the editing process down if your machine is not capable of handling the demands that they put on the process. That said, I know that many here who use Lightroom swear by it and do practically all of their processing and printing from it. I find the Adobe raw conversion to be average to good for most images, although the Adobe Standard color profile tends to be over the top for many conversions.
Bottom line - you have choices. If you are going to reevaluate your workflow and change applications, I would suggest you look at Iridient Developer for starters.
Best of luck,