Here's how I see it (it's okay to disagree):
1. God only knows whether or not, in 2 years, games will be optimized for hyperthreading.
2. God only knows whether or not, in two years, whether the i5-4670K will be the bottleneck for gaming.
Again, IMO, too many ifs to warrant the extra 100$.
Processors can be resold/reused too, if the computer isn't upgraded by then.