The 8 core won't be out of date by the time it's fully supported.
Six core support is almost the norm now and the Westmere Xeons and the 980/990X are far from what I would consider to be out of date.
TBH the only thing that will quickly be out of date will be the GPUs. 4gb in my humble opinion is not going to be enough as we go into the future. The new consoles have a unified chunk of memory, but 2gb of the 8gb goes to the system and the rest (up to 6gb) goes to the graphics subsystem.
This is why the last couple of games (Titanfall is one I mention here) use quite a chunk of vram. Even more so when you go 4k.
I wanted my rig to be 4k ready so I went with two Titan Blacks. Yeah, they may be a few % slower than the 980 and more expensive but I get to sit and laugh at the 980, given mine has more vram.
Nvidia are really, really tight with vram and always have been. My 295s had 768mb or so each and as soon as BF3 came out they were turned into very pretty paper weights.
So, I would pick the CPU you want (only you can decide on that) and for now go with a couple of cheaper cards (970s or 290s would be perfect IMO) and then wait for the real Maxwell cards (980ti? Titan 2?) and then invest in those.
That means IMO avoiding the 980 as it's not what I would call a reasonably priced stop gap. Of course, you could invest in a pair of Titan Black like I did, but with Maxwell 980ti or whatever it's called being reasonably close it may be a mistake.
I bought mine a good three months before Maxwell mid range came out, so I don't regret it at all. They have more than enough horse power for any game I throw at them, regardless of the few % loss they apparently have in benchmarks vs the 980.
If you want vram on Nvidia be prepared to pay for it. They're not stupid they're a very clever and shrewd corporation. They don't ever give away anything unless you pay for it, and they want you coming back.