Get a PS4 when the Slim is out or it sees a price drop in 2015, but redeem your free games using PS+ in the meantime to your account.
Honestly? Get a Vita. If I had the sense to buy one when it received a price drop, I would have enough free games to justify the purchase through PS+.
I also don't see the need to upgrade a PC every two to three years. What are you playing on what resolution that needs so much power?
Personally, I buy multi-platform titles on the PS3 and get exclusives for the PC, and later on double-dip for the multi-plats if they appear on Steam and have a nice sale going on. Its easier to re-sell the ones that are popular and because I don't buy on launch day, usually, I can get half my money back if I trade it in for something else.