I wonder as a PS+ member, who will not have a PS4, if I can still somehow add the free PS4 games to my account, so that if I ever do get a PS4, they will be instantly available to download.
I'm hoping so. I know currently you can "download" a free game, cancel the download as soon as it started so it's never installed on your PS3, but available to you after the fact in your PSN "Downloaded" list to "re-download" later. I've been doing that bit.
I haven't tried it with Vita games though, since I don't have a vita, but that should work since they install on the PS3 to be dumped across. I think. So I'm guessing the same thing should work for the PS4, unless you can't access the PS4 part of the PSN without a system.