is there a version of the iPhoto app for 64bit? and if not, will there be one available and when?

There will be no further development on iPhoto. Photos has replaced it. To convert your library to Photos:

Launch Photos with the option key held down. From the resulting dialog, choose your iPhoto Library. Photos will make a new library from your iPhoto media.

iPhoto was discontinued 6 years ago. It is no longer developed or sold. It was replaced by the more powerful (and free) Photos.app that comes with the OS. You can migrate to that app very simply:

Hold down the option (or alt) key and launch Photos. From the resulting menu select 'Choose Library' and point at your iPhoto Library. It will do the rest.

If you prefer not to use Photos there are several 3rd party apps that you can use. Which to choose depends on the kind of photographer you are and your budget.