Let's talk about the rise and the fall of the 2Gate strategy, because I think that discussion will enlighten you as to the strengths and weaknesses of blocking as the entrance of the natural.
The 2 Gate strategy was developed near the end of the Beta, largely by a player known as Tester. Tester's strategy revolved around using the two Gateways at the entrance to the natural into early pressure. This was a reaction to many Zerg players at the time going for more Zergling centric builds after a series of Roach nerfs.
By placing the Gateways in a "wall" he could stop any counter pressure from Zerglings, allowing him to take an early expo and possibly deny the Zerg player's expansion (putting him a base ahead). Since Zerg usually rely on base advantage this was a very strong build. What's more by using warp technology he could warp in units outside of his wall while using a single Photo Cannon to stop any Roach pressure (as even at max range the Photon cannon could reach the Roaches if they attacked the wall).
Thus Tester would have a safe, early expansion.
So why don't more Protoss go for 2 Gate pressure against Zerg? Well partially nerfs to Zealot production mean that Protoss couldn't apply pressure as affectively, but a recent change to Roach range really cut down the effectiveness of walling in. Because Roaches now have a range of 4, they are capable of attacking the Protoss wall without taking Photon Cannon fire. As a result building a wall at your natural suffers from exposing your production facilities to harassment, while blocking off your own ability to quickly reinforce from your front to your main. This is the same problem as walling off at your main.
Does walling have a future? Well a discussion of the history and its roll in the meta game (and why the Roach range buff was so important to Zerg players) is very important so that you understand how these factors contribute; however, that doesn't mean you can't. Walling at the natural provides for the same buffer against early Zergling pressure, and is useful to 1 Gate Expand, style builds. Additionally, Terran players can use the ability to lift off to remove the exposure latter in the game when the wall stops being beneficial.
Do I think that walling at the natural has a place? Yes. Do I think it'll become standard? Based on the disadvantages I've listed, probably not. I think its definitely something you should explore and that it'll come back again in a serious way.