More Tiers?

Perhaps there can be more tiers in the game? Just encase somebody "completely" finishes the game (as in having everything) and needs some more challenges.
Maybe there will be more tiers in the full version, but it would be nice to have more of a challenge after Tier 3.
Wait for The Core.
And good luck fighting through the Firestorm Citadel.
I'm sure they are developing more tiers or have plans for it in the future. What you're asking is that they expand the game. Something they will worry about when we are bored and plowed through the content already available to us.

As long as the demand is there and people keep progressing, I think we can expect some kind of T3+ in the future, I think we should be worried about getting to T3 and the Core first anyways and then go from there.
I'm sure there are more areas and gear in the future of Spiral Knights.

Personally, I had many of the weapons (Guns, Bombs, and Swords), but I always found it fun in general just repeating runs and such because its always fun with friends. I have to admit if there was a T4 or even T5 you have to imagine we would have 6* items or higher which I dont think this game is ready for currently because that is a BIG CHANGE. Vanna and Firestorm is pretty challenging for most players. Personally, I fine Firestorm pretty FUN =) so much heat and its really fun only because there are small mini games and strategy is needed.
They can Keep only 3 tiers. What they can do is create new bosses of different element like vanaduke being undead/fire and even more challenging gates which requires a good cooperation of your party just like puzzle. I found one gate where you needed to figure out the order of hitting buttons to open the gate.
My thoughts exactly.
Now, granted the testing we saw was highly accelerated because energy costs on elevators were dropped and people were giving things away (including energy) because of the impending reset.
The actual game should progress a lot more slowly and you probably won't be on tier 3 within a week.
Still, I don't ever want to hit a point when I don't have a reason to go on a run. If the game ends at the core, I will be very, very sad. The game play is amazing, but I still need some kind of carrot on a stick so that I can feel fully justified in spending my time in the depths.