I have a Late 2011 MBP15. I upgraded the RAM to 16 GB, installed a 1 TB SSD and replaced the DVD with a 512 GB SSD years ago. I got a thunderbolt dock to get access to USB 3. I have been waiting for a 2 years for a new MBP that I liked.
I like the new MBP 15. I'm happy with USB C, and happy that Apple didn't add ports that won't be used in 2 years. I could care less about the the touch bar, and the keyboard is OK. The CPU power looks good and I could live with the GPU. I don't understand the why everything needs to keep getting smaller but ok. I don't buy a laptop because it's thin, I buy it because it does what I want and it's "thin enough"... I don't think Apple understands that. Personally though, I just can't bring myself to spend between $4,000 - $4,600 for a MBP that only has 16 GB of memory, a middle of road GPU and because everything is on system board, WHEN something goes bad I'd guess that any repair is going to cost as much as a replacement. I decided to wait until the end of this year for a better option from Apple. If things don't get better, I'll hold on to my late 2011 MBP 15 for iOS and Mac OS development but end up moving back to Windows for everything else (Yuck). Apple really is charging twice what you'd pay for a very nice Dell or Asus 15 inch. My guess is that by June $2K will get you equivalent spec'd hardware with 32GB of memory and better GPU, not as nice of a feel, but the same or better performance. I'll buy a 4K or 5K display and save the other $1,500.... I'll just have to live with Windows. Microsoft Office and Adobe offer their products as a service now. I can also access music and video content with streaming services so although I might have thousands in iTunes, I can still access all the same content via streaming services so I'm not locked into the platform like I used to be.
It's hard to say what I would do if I were you. However, if you are dealing with large images and 4K video I'm not sure the Air has the horsepower or internal storage that you need. A dual core i5 and 128 or 256 GB of storage is not very much. You could go external storage but that will add to wait times.
How bad do you need something now?