I keep watching this thread hoping it will come to some sort of conclusion but I'm beginning to think that won't happen.
As far as I'm concerned, the DLC was (probably) going to happen whether we made it to the £2 Million mark or not, all reaching that point did was ensure that Kickstarter and PayPal backers would get the first DLC pack for free.
Playtonic no doubt keeps an eye on these forums and has already heard the opinions of those of us who've made our opinions known regarding DLC, and I'm sure they'll make the right decision based on those opinions of what that DLC will entail. As things stand right now, we have absolutely no idea what they might plan down the road to make for the game as DLC, it's all purely speculation, possibly based on what other companies have done with DLC for their games. I can't think of a single 3D platformer collectathon game that's been released that later had any sort of DLC or expansion pack, so as far as I know there's no direct comparison to even begin to more accurately guess at what Playtonic could create as potential DLC for this game.
Additionally, they're not even going to be planning what to make as DLC for the game until after the game is complete and available to backers and non-backers alike (at least, that's what they said regarding it during the Kickstarter campaign, and I for one believe they're telling the truth and will not be planning anything or setting ideas aside to use as DLC during the game's development). I'm also sure that, when the time comes that they've completed their first DLC pack for the game, they'll price it fairly based on what sort of content and how much it adds to the game, and will not overcharge for it as a way to make a few quick bucks from people willing to throw their money at it.