If you have a ps4 already you can enjoy it on there and if you decide to upgrade later then you can. Not like it wont work on a ps4 now.
Besides thats rumors. ps4.5 wont be an all new experience, I think its mainly aimed at bringing 4k gaming to consoles. Even then it wont be true 4k, probably be more like what up scaling does for dvds, it helps but doesnt make it like a whole new experience. We wont see a true 4k console till the next generation.
It will probablly be like a pc in the sense that you can run any pc game, but if you have a more powerful gpu you can bump up the graphics options a little. Im guessing it will be something like that since sony would commit suicide financially if they cut out the 30+ current ps4 owners from being able to play games. Then they would probably phase out the current ps4 to make the transition seamless as possible.