Talk about a multi-purpose rifle! What will they think of next?!?!
To the OP--If you know you are going to own one at some point, then go ahead and buy the ammo when you find it. With the current political and/or sociological changes that may come, you'd hate to buy the rifle and then find that you can't get any ammo for it down the road.
I was in the same boat with .45 ACP. Had a gun stolen and knew I was going to get another, just had to find it at a good price. Still stocked up on ammo and components when I had the chance. Finally found what I wanted in a firearm and have plenty of ammo on-hand or ready to reload for it.