While i do agree that this will allow players to live much longer, I don't think this will hurt combos a lot. What a lot of people don't seem to realize is that you CAN get out of combos in Melee with good DI. If the opponent made the wrong guess of where you go after a move, you can get out of combos.
The same case with Brawl, despite combos being ruined by airdodging out of combos, you just need to guess where they go and follow up.
In Smash 4, despite the pros and cons this mechanic offers, this mechanic will courage more players to play off-stage to get kills.
The game has only been out for a week to a week and a half, and most players hadn't took advantage of the new ledge mechanics yet. CT Zero is one of the only few that has took advantage of it, and man, those matches end really fast because of that and are fun as hell to watch the ledge mechanic being used by professionals.
I don't like how a lot of people are judging this game and instantly call this game Brawl 2.0 when they either hadn't played it themselves or whatever. Give the game more time so we can see how much the meta for this game evolves. From what I've seen from early tournaments, the game offers a lot of diversity and most players are starting to take advantage of the ledge mechanics and the game has recieved lots of positive reaction from the competitive community.
You also got the recently discovered "Rage Mechanic," which, while I find it odd at first, could possibly counter this mechanic a little, but I'm not sure at this point.
I know many will get mad at me for saying that, but this is just me giving out my two cents out there and small rant. I've been playing Smash bros since the first game, and trust me, you really do need to guess where the opponents go in your combos. Otherwise, they will get out of it.