The 8 core Exynos procs Samsung is using now only give you quad core performance. Essentially (and as simply as I can put it) there are 2 sets of 4 cores. One set has a power restriction on it, and the other is full throttle. If the phone does not require tons of processing power, it switches to the low power set of 4 cores. If you're loading up a crazy game that's going to need the processor to work very hard, it'll switch to the other set of 4 cores. In any event, you'll only be running at quad core speed at any point in time. There are no points in time where all eight cores are being utilized.
Furthermore, the amount of apps on the Play Store and Amazon App Store that support quad cores is only a fraction of what's out there. There are no apps optimized for more than four cores, so having eight cores wouldn't do you all that much good. You could put in 120 cores and that doesn't equal speed. I believe we're at the point where we need to work on efficiency and software tweaks rather than to further processors.
What we REALLY need to work on, is battery tech. We have 1080p screens, quad core plenty fast phones, now awesome speakers, good frame builds, where's the battery for all this stuff? Everything in that list of great hardware relies on the battery to power it. Batteries should be the focus from now on IMO.
Anyway, the point of all of this is just buy the damn phone. You'll like it and nothing crazy astounding should be out in the next six months. Maybe a new Nexus device or something, but nothing groundbreaking.