I am a hardware guy. Cooling would be a small issue (but additional die shrinks may make it possible)
There were 3 generations on Xenon which powered Xbox360 (90nm (2005), 65nm (2007), 48nm (2010+))[1]. Modern processes are 28, 16/14 (10nm is Intel only really and Xenons were fabbed GlobalFoundry) [1]. The 2005 vs 2010 models reduced power consumption reduced power consumption from 177watts, to 88watts (under intensive gameplay) [2].
So realistically there are 2(ish) nodes available 28nm and 14/16nm [3]. Which could likely (best case scenario) halve power down to 50-40watts. Apple TV by comparison uses 1.8watts [4]. Passive cooling is possible, but the case foot print would be larger.
[3] 14nm/16nm are 28nm but a different gate style. Features are still 28nm. Also I'm assuming GlobalFoundry is calling their 45nm node 48nm because they called their 14nm node 16nm.
Those are stats for the Apple TV third generation. The fourth generation is significantly different and uses more power but it's hard for me to find an exact official number from Apple. I don't think it's much more though.
There were 3 generations on Xenon which powered Xbox360 (90nm (2005), 65nm (2007), 48nm (2010+))[1]. Modern processes are 28, 16/14 (10nm is Intel only really and Xenons were fabbed GlobalFoundry) [1]. The 2005 vs 2010 models reduced power consumption reduced power consumption from 177watts, to 88watts (under intensive gameplay) [2].
So realistically there are 2(ish) nodes available 28nm and 14/16nm [3]. Which could likely (best case scenario) halve power down to 50-40watts. Apple TV by comparison uses 1.8watts [4]. Passive cooling is possible, but the case foot print would be larger.
I'm not a thermodynamics guy.
[1] https://en.wikipedia.org/wiki/Xenon_(processor)
[2] http://www.anandtech.com/show/3774/welcome-to-valhalla-insid...
[3] 14nm/16nm are 28nm but a different gate style. Features are still 28nm. Also I'm assuming GlobalFoundry is calling their 45nm node 48nm because they called their 14nm node 16nm.
[4] http://www.flatpanelshd.com/review.php?subaction=showfull&id...