Dual core is more than sufficient for your needs. Processor development is way out front of 99% of all software currently being used. Nonetheless Intel's got to sell their products just like everyone else, no matter how irrelevant to the needs of the majority of users.
Also here in our "consumer" oriented society we're programmed to desire the latest, the fastest, the most power, and on and on.
The software you listed cannot even take advantage of a quad core processor anyway, so in your case it's a complete waste of money. As far as the concept of "future proofing", that's a myth. The development & product cycles are so short there's no way to effectively future proof any computer for any significant period of time. It's money wasted.
That said, what works for you today will work every bit as well in two or three years, unless you have some massive change in your needs. I say, buy what suits you today and worry about the future when it arrives.
You may find it's not the internal specs you want to change but the model, ie: MBP to MBA. By not overspending only to find you are not using all the capabilities now, save your money for the next one.