Why to revive Thief which didnt sell as hot as Splinter Cell? Thats because we already have a stleath game in modern setting.
Also, I personally do not think T3 bombed. Neither did DX-IW. If they were, EIDOS wont think of making sequels [and thats the reason why games like Torment or NOLF2 dont get sequels] Both games sold atleast reasonably well and there definitely was enthusiasm amongst gamers regarding both [mainly for DX-IW], but they both suffered from consolization and relative departure from familiar gameplay style of previous games. EIDOS now is taking chance to correct thier mistake [or atleast giving us hopes for the same]
What exactly you mean by 'ego' of T3 developers? The team had many ex-LGS'ers (though lead designer resigned shortly before game release) and I am sure they did their best within given constraints. Like someone else mentioned, the game got flank mainly coz of ultra tiny levels which took away all the fun in an otherwise good game, and that was coz of stupid xbox memory size limitation. Certainly, the decision of developing the game on XBOX alongwith the PC contributed to the 90% of the problem. One can edit ini files to remove loot glint, arrow trails and such trivialities that bothered some 'hardcore' fans, but nothing can be done about level size. Yet still, there were good levels like Cradle and Museum...so in effect, its the multiplatform problem. Indeed, a game can still be as 'complex' as they make even on XBOX, but the gameplay of DX and Thief inherently require good enough level size [with thier goal of solving problem in multiple ways, taking multiple routes n all]