I've played the game since launch. It has many good things a a few problems that will get worse down the road I believe.
1-Cast system is second to none. Not to bash WoW but Rift kills it here. WoW forces nearly all talent points into one tree. Very sad. Rift you can put talents anywhere you wish in 3 different trees at once. Did they steal talents from WoW? You think:P
2-Rifts are a great idea. They can pop up right in your way. They can spawn invaders that can even take over quest Hubs. Again WoW has nothing. What you see is what you get nothing changes.
3-Zone wide invasions. These are plain fun. Great way of having somthing different just pop up at any given time. WoW? again nothing. You go through a zone and what you see is what you get it never chances.
On the above 3 Rift just kills WoW. They are what will make or break Rift. Why? There is nothing Rift does differently in the other parts of the game that are any different than WoW.
Troubles I see coming.
1-Rifts. 90% of the time now on my server no one stops to close a Rift. In the beginning you see people ride for miles to close one. Now? You'll be lucky to get anyone to close one. Rift needs to bring back that. Rift is the name of the game. Rifts should give rewards so you'd want to close one not ride by. Maybe 1000 bonus EXP for being there and closing let's say most of the minor Rift. Maybe a major would give 4000 bonus. Maybe a very rare chance of a Armor drop or a weapon, trinket ring. Something good but very rare. Think of the people who even today in WoW do Baron run just to get the mount.
2-Invasions. From what I see now even thou Rift has tried to make what you need to do easier people still will ride away from a Stone even thou there are 4 invasions 3 steps away. Don't see what they can do to change stupid. Maybe have them spawn in parts like epic invasions. First up defend a stone then part 2 pops up and you close 10 rifts.
3-Invasions spawns. Here is real trouble. I level from 1 to 20 and never saw 1 invasion. Was I unlucky? Maybe. But when they are spawned because of zone pops and there are none in the zone you never see one. If a GM forces a invasion it fails because there aren't enough in the zone to do it. People there just log out until it's over because they know it will fail. Yes Stillmoor works. Force a invasion and people come running. But in Freemarch? Why would a level 20+ come back to help? Not worth the time.
4-talent trees. I can see it coming and it will. Nerfing PvE because of PvP. It killed WoW for me. And some classes in this game are so over the top in PvP Rift has to nerf them. This hurts in PvE because of PvP. Which is bad.
Rift does have a future. What it does better than WoW are why I left WoW. Because Rift needs to get a handle on a few things I've listed or slowly it will die when it becomes WoW without the 3 things it does best.
Ok I'll turn off the wall of text now:)