This makes zero sense and will never happen, for numerous reasons.
1: Relearning perks is not logical. Taking a perk means you take on that knowledge, meaning you "learned" it. You can't just "forget" things.
Say I want to go to college to be an electrical engineer. Say I've been an electrical engineer for 10 years. Well, all of the sudden, I want to be a zookeeper. I cannot just "forget" how to be an electrical engineer and then suddenly be a zookeeper. Life doesn't work that way. You don't just forget things. That doesn't make any sense at all.
2: Crafting. Say you completely deck out the Smithing tree, get ALL the perks, Smithing at 100, you craft dozens of pieces of high quality gear, you improve these pieces via the tables and grinders, and then BOOM! You forget how to do that? So what, you crafted legendary items and then you lost the ability to do so, netting you essentially items you don't know how to make? That makes zero sense. It doesn't work like that. It would also be absurdly overpowered, considering you could just "get" the best things and then "lol sorry I wanna be a CHEMIST DUDE" and then "respec" to being a master potion maker? No.
3: Choices need to matter, live with the consequences. When you make choices in this game, they *should* matter. Making this game an MMO where you just flow with the wind and do whatever you want without consequence is not a fun way to make TES games. People want choices, people want things to matter. That's why there are so many threads on the boards about how completing quest lines don't matter at all, and it impacts the game in no way. That's not right, and people don't like that.
4: Replay value. Reallocating perks would *kill* replay value. If I wanted to just switch "specs" and be a mage, I could do that. That's absurd. This is not World of Warcraft. If you want to be a Mage, be a Mage. If you want to be a Warrior, then make a Warrior.
So yeah, perk changes will never happen.


Seriously though, respecing perks makes no sense, and I hope it is never implemented.