I would like to get The Binding of Isaac for with this months PS Plus membership. However, I don’t plan to purchase a ps4 until March. Could I buy a PS Plus membership, go to the playstation store website, and secure my purchase of the free game without actually owning a Sony console yet?
I can confirm that this worked for me on the Vita before I bought it.
I bought my Vita last year, in March, and was able to go to my download list and download PS+ titles for Vita that I had associated with my account the previous fall.
It should work the same way for the PS4.