While I personally agree that we should not store all transactions for all time, our storage capability is going to get exponentially better. We are able to store data in 3D discs with lasers now and can store petabytes in a single disc the size of your typical old CD-ROM and even store data in DNA if we wish. These obviously aren’t going to be included in your desktop computer anytime in the near future, but they do currently exist and show that storage will not be a problem for a very very long time.