ONE CONSOLE WORLD!
With current technology, it's almost viable -- given a set of properly modern hardware specs, it'll take at least 8-10 years to really wring the juice out of it. The complexity of a forward-minded modern hardware specification is going to tax the current dev set, and not having to worry about ports lets them focus on doing just that. HARDWARE competition isn't necessary, since I don't feel growth needs to happen as fast as we're really hitting the limits of current TV sets.
Look at the hell of the PC video card market -- loads of features that are sorely underutilized on the top-of-the-line cards, suboptimized software, visual bugs/glitches galore, and massively inconsistent frame rates. Too much competition isn't necessarily good in a qualifiable sense, unless benchmarking is your primary source of entertainment in this industry -- current PC game feature sets lag five years behind the hardware, and a $300 card, despite being a monstrous deal for the level of technology, is victimized and castrated by shitty software and APIs. Xbox games, resolution issues aside, LOOK as good as the average high-end PC to the general consumer (note: not benchmark/screenshot whores) -- can anyone REALLY argue that the difference between Rallisport Challenge Xbox and RC PC on a high-end system is as massive as the disparity in specs might indicate?
Of course, the ONE CONSOLE WORLD doesn't change the important area of competition: SOFTWARE DEVELOPMENT. With no radical hardware configurations to port to, devs can focus on creating the best and the least buggy content out there.
Best of all, if the ONE CONSOLE SPECIFICATION focuses not on set-top shit but on a core set of multimedia functions, there's no excuse like NINTENDO FAILED CUZ EVERYONE WANTED DVD!!! Some ONE CONSOLE SPECIFICATION implementations will have set-top software features external to the core multimedia functionality (like Media Center features) at an added price (to either the user or the manufacturer), but that sorta competition doesn't hamstring developers and create such a fractured software environment.
On top of all that, first-party accessory/peripheral manufacturers will lose their stranglehold. FUCK YOU $40 MEMORY CARDS.
The only compelling reason to have a multi-console world is for historians and collectors: quirky hardware and variety always make for a little color. Not that the ONE CONSOLE WORLD isn't a dream riddled with flaws -- developing a common hardware specification and APIs is a task I sure wouldn't want -- but in the end, with a proper hardware leader (Sony or MS), it could theoretically happen and I think we'd all be the richer for it.