Pantheon is likely to fail, or at the very least be a very niche MMO. But maybe a very niche MMO is good for some.
For example, these are the reasons it is very likely to fail:
Launch release (1 month in, 2 months tops but will already have lost a lot of players) not perfect? As vanguard saga of heroes showed, if release isn't perfect and even if the game gets fixed, and most will never go back to it again. This makes finding groups VERY hard except at only the latest levels, and anyone joining the game later in life won't be able to do content since its all group based.
Next, again Vanguard being a great example (it WAS the MMO made for people asking for an oldschool experience)...
Vanguard was by far the best MMO (thus far that has been released), but despite everyone on MMORPG.com asking for an oldschool MMO, no one on MMORPG.com was interested in playing it. Sure launch was bad, but that is like getting a piece of cake at a restaurant and having a fly inside it. Instead of asking for a new slice of cake, you'd storm out the restaurant and never go back even if its a restaurant you've wanted made in your neighborhood for years or decades. Most people who REALLY wanted that cake and wanted that restaurant open, and enjoy that flavor of cake would instead ask for a new one slice, not leave and enjoy a brand new slice of cake.
So, since no one enjoyed Vanguard, nor even gave it a shot after launch...that is a HUGE sign this kind of MMO is not wanted, even by those on MMORPG.com asking for an oldschool experience. Why ask for years for something, that something comes out, but not actually play it? If my dream game came out, warts, problems and all, I'd stick it out and if it did improve and I took a break, I'd go back. Obviously this means no ones dream game (very few anyway) is an oldschool experience. Because if it was, they'd have enjoyed Vanguard, the MMO made for an oldschool experience.
So, did Vanguard show that people don't REALLY want an oldschool MMO? Cause if I asked for years for a game to come out, and it was my dream game, I'd definitely play it especially if any bugs came out.
And if pantheon has any problems at launch at all, it will very likely follow in Vanguards footsteps because no one tries their "dream" game twice (which sounds like an oxymoron, if its your dream game, wouldn't you play it?)...
Now you may think this is a negative thread. But in fact it isn't. Vanguard was by far my favorite MMO, and it was incredibly sad to see it die. However Pantheon can be successful if it thinks itself a very niche experience, since most obviously don't want an oldschool experience (which is sad). Pantheon is my most looked forward to MMO coming out, and if its anything like vanguard, it'll be amazing.