Considering that the Dark Souls games have become popular for many reasons including a fluid combat system. Can Bethesda try to improve their combat mechanics. As one person said "The combat in TES games makes you feel like you are slicing air." What can TES learn from the Dark Soul games?

Little to nothing. The Dark Souls games are a radically different basic foundation than TES, and trying to take what they do as an example of how to approach things in TES is frankly a horrible idea. At best, TES can learn from better use of weapon-hitboxes instead of point-targeting, but that's about it. And there are far better examples of that in other games anyway.

Even then, Dark Souls combat isn't really that great. It's very much in line with the style of games like the Arkham series, Shadow of Mordor and even Ryse, in that you ultimately lack much in the way of control and are entirely dependant on how the developers decide a weapon fights like. Many of it's very flawed combat mechanics are made apparent in PvP, where light, fast weapons and often no armour at all are overwhelmingly common, because they are the most successful.

Ideas and suggestions for future TES games can be discussed here: http://www.gamesas.com/topic/1605572-official-beyond-skyrim-tes-vi-86/