Hello.
The devlopment version (2.3 dev) support widescreens. It use anamorphic format, or real widescreen (geoscape, battlescape), according to the GUI window you are using.
You must chose the resolution you want into the right option window. And uncheck the "force 4/3 ratio" checkbox. Maybe unckecked should be the default value, but it is not yet the case.
For the engine, there is no chance 1) it need too much work to switch to another engine 2) and the engine is highly modified, and continue to have update. 3) Then there is no absolute need, but we can talk about features.