I'm not really sure what you mean by, "is it still going to sound when I try again to use that voice", but the thing to remember is that, when you store your keyboard settings in a registration, you are simply saving a list of all of the parameters (that the keyboard allows you to store in the registration) that you have set up, such as the sound of your main voice, the sound of your dual voice, the sound of your split voice, the settings for your style (such as which style number and the tempo), and any sound enhancements (like reverb and chorus) that can be stored. If my experience is any guide (and I seriously doubt that they changed this), saving anything to a registration in no way affects the characteristics and timbre of any of the keyboard's preset sounds that you may be saving to that registration.
Those sounds, along with any applicable S.Art Lite features associated with them, are hardwired into the keyboard and cannot be permanently changed even if you wanted to do so, and you are free to use those sounds as often as you want in as many registrations that you want -- up to the limit of the number of registrations your keyboard allows. You can make enhancements to the sounds, such as adding chorus, reverb, and (I believe) special DSP effects, and then save those enhancements to the sound to a registration, but doing this does not permanently change the characteristics and timbre of the preset sounds that you used. When you store the sound to the registration, you are NOT telling the keyboard to make permanent changes to the original sound -- you are simply storing the instructions to call up your desired tones and make your desired enhancements to them, just like you would do manually by selecting a voice number and turning on features like reverb and chorus -- but now, with the sound stored in a registration, calling up the registration just virtually "pushes the buttons" to call up the voice numbers and sound enhancements you select. But again, none of this permanently changes the original waveform, timbre, and S.Art Lite features of the voices you use.
For example, let's say you select a trumpet sound. When you first call up that tone, it will sound a certain way. Now, let's say you add reverb and chorus and make that trumpet sound like a nice, echo-y, swirling synth-type sound. Now, if you like that sound, you can save it to a registration, so that you can call up that sound -- the trumpet along with all of the sound enhancements you added -- with the push of a button. But saving this sound to the registration in no way changes the waveform or timbre of the original trumpet sound that is stored in the keyboard in the keyboard's list of hundreds of preset sounds. If you turn off all of the reverb and chorus and other effects you may have switched on, and then call up the trumpet sound again (by selecting it from the keyboard's preset voices, not from your registration), then it will sound just like it did before you applied the synth-type-sound modifications and stored your registration. But if you then call up your registration, you'll get the modified synth-type trumpet sound that you created by adding all of the special effects, because you stored all of those effects, along with the trumpet sound, in that registration.
Think of it like storing a word processing document on your computer. When you save the document, you are saving a collection of all of the letters that you used and in the proper order to make up the words of your document, as well as any important characteristics such font size and spacing. And maybe you are applying modifications like bold-face and italics to some of the letters. This would be like storing a registration on the keyboard. But just because your document that you saved to the hard drive may have had the letters, say, "a" and "n" in them in bold-face or italic, that in no way affects your ability to use the letters "a" and "n" again to type up a new document, and it does not change the appearance of those letters when you use them in a new document. The appearance of those letters, without the modifications like bold-face or italics, are stored in your word processing program, and they will not change just because you added "enhancements" like bold-face and italics to them when you typed up and stored a previous document. So, in a similar fashion, the preset sounds of your keyboard are stored or hardwired in the keyboard and will not change just because you previously applied sound-enhancements to them and stored them in a registration.