When you are compiling the kernel, you have a choice of either starting from scratch, or using your existing .config as the default starting point. In either case though, you are free to make any changes you wish, including configuring all those cool new features. So, if you are really asking "Will using my existing .config file prevent me from making any changes to the existing and/or any new parameters?" the answer is No.
Basically, from my point of view, using the existing .config file is a huge time saver, and it minimizes the chances that in your enthusiasm to compile that brand spanking new kernel, you inadvertently turn off or forget to set a particular parameter, which in turn causes problems for you later. In other words, your existing .config file is your friend - it can really help you out of a jam if the recompile doesn't work out quite the way you expect. Lastly, along these lines, it's always a good idea to keep copies of both your existing kernel and its .config file, just in case you need to restore things. Trust me on that point. -- J.W.