Hi. That is not required with 16GB, but that processor would speed up a little the machine. I bought the max out version (2.8/16/1TB) trying to be future proof like you, so my recommendations may be somewhat bias
Anyway, don't know if you are buying new or refurbished, but would highly recommend you check refurbished machines from Apple, since they come with the same warranty as a new one and at a reduced cost. My current 13" rMBP is not a refurbished since bought it shortly after they were released, but have previously purchased refurbished with great results. Also check Amazon warehouse deals, as I bought my daughters 13" rMBP there for a great price as well.
Regards,
Francisco