I have a different take. iPhoto appears inside your purchases attached to your apple id. I don't think that apple will be taking away your purchases when a new product that has since come along has replaced it.
I have 2 mac's. My iMac is running in Yosemite and the mini seems not to like that version of OSx so I have left it back in Maverick. my Apple id is used for the appstore on both machines, and the version of iPhoto that works wit Yosemite doesn't work in Mavericks, but apple does know that and will only let me load the correct version to each mac.
Now if they took away iPhoto and replaced it with Photos, they would need to develop a version for every mac OSx version that could run iPhoto. That would not be worth their time. So iPhoto will just sit as it's own app on the appstore and if you have purchased it you can still re-download that from the app store. But any new customer who has never had iPhoto wont see it as apple doesn't sell it or really support future development of it any more.