It strikes me that TW is becoming more and more diluted with the creation of new worlds seemingly every couple of weeks. I myself am quitting due to the time it takes to maintain an account at a competitive level. I watch many players come and go, I cannot ever play TW again without a coplayer, the sacrifice is far to great otherwise.
I must say that under the current management of TW, that a world without coplayers wouldn't do anymore damage than any other new world and settings. However, I would rather see TW promote the life of a world, rather than the mass releasing of worlds upon worlds upon worlds. It strikes me that 17/18 were the last of the epic worlds. The game is losing it's flavor, as all games do that deviate from the ideology that makes them great.
I do believe that a world without coplayers will limit competition. Some people, many who have given years to TW use coplayers now as a way to continue playing the game, while still remaining competitive. To lose that core of players to a new world will create much larger disparity between super-active and casual players.