I've gone from a 13" MBP with TouchBar to a 12" rMB. I don't miss the TouchBar as such, but for what its worth, i don't think its a gimmick - its got a lot of potential and depending how you use your Mac it might me a good time saver in certain programmes. I do miss TouchID although that was frustratingly under-used in the current OS. I was looking at buying a big monitor to go with it and using it in clamshell mode which seemed like a bit of a waste, so I sold it and picked up a second hand rMB and a refurbed iMac.
Previously I had an 11" MBA for 3 years and I'd obviously underestimated how much I liked having an ultra portable laptop. Like others have said, computing has changed a lot in the last while and the previous arms race scenario of more memory and higher clock speeds is kind of irrelevant unless you're a coder or video editor who absolutely needs lots of cores and high performance.
I bet for the majority of users any current Mac with an SSD and 8GB will last for years. And this is coming from someone who had to have the fastest of everything with the most RAM etc.
Battery-life wise the rMB also seems to be on a different planet compared to any of the new MBPs but I guess that's to be expected given its design. The new 13" MBP is a lovely machine, so go have a look at them in the Store, have a play and see what you think.
I wouldn't be put off by buying a rMB now in case it gets updated soon though - like other Apple products, I don't think the new one will be revolutionary and the current one should still last for years. I totally get why people want to wait for the next iteration of something, but i've been there posting in "next version" threads from the start, for months and sometimes years when I could have just bought something and been actually using it for months and years instead of waiting and speculating.