I can't imagine a game that enjoyed both critical and player success as well as financial success would not be considered for a sequel. I'm actually surprised nothing has been anounced about such as yet and further, that there haven't been any expansions/DLCs (since Missing Link).
The game, in my opinion, was a master piece. It had some flaws, yes, but none of them could detract from the overall whole. The non-optional boss fights with, as Yahtzee suggested, uncharactarised antagonists, the jerky character animations, the gold colour filter over everything and the always-annoying "ending machine" that I believe detracts from the choices made throughout the game. The endings could've been better and my only other criticisms are the same as I would have for any console-developed game that's ported to PC...too consoley (small maps with frequent load screens, 7 year old graphics, etc). The press-button for cut-scene takedown I would prefer to see gone too, in lieu of actual melee weapons.
But these flaws are nowhere near enough to put it in the "flawed gem" category, with Alpha Protocol, VTM: Bloodlines and the ilk. The gameplay, characters (not the mercs), pace, ambience, story were brilliant. It was polished like a mirror and a tie (with Skyrim) for best game of 2011 (and 2012 as well, since there hasn't been anything this year to come close to either of those). I wish they had finished Montréal as a third hub city and would've loved more content, more story, etc.
I would love to see a sequel, and suspect we may see one in the future. But in the meantime, I *believe* it's the same team at Eidos Montréal working on Thief 4. As long as they kept the original voice actor of Garrett, I would punch a hundred hobos [http://www.youtube.com/watch?v=qLIHnWxGj_s] for a copy of that game!