I've also been evaluating skylake, and I'm a little skeptical about those rosy performance numbers.
If you look at a full comparison between the 6700k and the 4790k, you'll note that most benchmarks show little to no change. There are exceptions: integrated graphics has definitely improved (but you won't care), and there are new instructions that improve targeted workloads (e.g. OpenSSL) - but again, that's not going to help the ruby interpreter. Also, exceptionally, the JS benchmarks have significantly impoved: Krakenjs for instance achieves a score of 735ms vs. the 4790k's 938ms. A whopping 28% faster at roughly the same clockspeed!
Now, if you disregard the anomalous JS results for a moment, there are other benchmarks that look at least vaguely like a ruby workload. For example, the dolphin emulator benchmark hopefully has some similarity - I think I'd pick that as my best bet barring an actual ruby benchmark. And you'll note that there the skylake advantage is much smaller; it's just 5% faster. Office productivity may also be roughtly similar; there we observe a 4% advantage. 7-zip compression shows a full 11% advantage, but that's highly memory-system sensitive, and I'm not so sure it's representative of your use case. Decompression is juts 6% faster. Redis is 4-17% faster (1x 4%, 10x 17%, and 100x somewhere in between). Agisoft photoscan's CPU mapping speed is another plausible best case, with a 17% performance advantage.
I really don't think 33% is realistic. I'd expect no more than a 5 to maybe 10% advantage at identical clockspeeds - of course, that's not quite the case for you, so that might add another 10% for you. In your case, you might hope for 20% improvement - but that's a little misleading because you're then comparing non-top-of-the-line haswells with top-of-the-line skylake.
I'm really curious what the difference actually turns out to be. Can you post some actual ruby benchmark numbers?