You don't need much of a computer for that stuff, you should be fine. I had a 2011 MBA with 4gb RAM and I ran Photoshop, Final Cut Pro, Logic Pro, Vetorworks, Filemaker Pro, MS Office and other software. It was the fastest computer I had owned up to that point, it literally ran circles around my 2008 15" MBP. I'm sure there was some swapping taking place when I had several of those programs open at the same time, but the SSD is so fast I never noticed it.
The current MBA has a faster SSD and CPU than my 2011, it also has faster USB and Wifi, and battery life almost twice as long. As long as the SSD is large enough for you needs, you should be fine. If you're concerned that future software and operating systems may not be happy with 4gb, then just don't update, I almost never update my computers from the version that ships with them.
