Prostalgic

a sentimental longing or wistful affection for the future, typically for a vision of what is likely to happen, typically accompanied with happy personal associations.

As I helped my father learn to use his new phone, I was overcome with prostalgia as I envisioned an older version of myself needing a similar level of care to master the holodeck. These prostalgic feelings almost always catch me in moments with my parents, especially now that I have a child of my own to track these passing years against.