They released the mission editor as a token appeasement to PC players who expect the ability to add their own content to the game, except aside from scripted enemy engagements and custom multiplayer maps (co-op and PvP) you can't add any user created content to the game, modders are definitely not welcome.
All the game files are locked away in a proprietary compressed format, no mod tools means no mods, no tweaks, no user created content.
You're at the mercy of whatever Codemasters decides to release for the game in the way of DLC packs and patches.
They have said they're working on a bug patch for the game but people are reading too much into it, I really doubt major issues will be addressed such as the lack of dedicated servers and the ability to join games in progress.
If they bolt on extra content to the existing game map it's going to get very repetitive and boring fast, the one large island map they created for the game just doesn't have enough variety in scenery and interesting places to explore - you can only do so much with changing the lighting and adding fog to a map to switch it up and make it feel unique. I think the one map approach was a poor decision, they should have broken up a bunch of different areas for maps much like GRID and DIRT have done - as well as other popular FPS shooters.
/long winded blah