Searching the web and the Android Team announcement I couldn't find The answer. Will Eclipse ADT be deprecated when Android studio reach its first stable version? The funniest thing is that they also update eclipse plugin to the latest ADT 22.0.0
Why the Android Team started another IDE instead of continue improving the old good ADT ??
It seems like yesterday when they announced the ADT Bundle with all the android plugins integrated.
Personally I could not find the right answer about this. To be honest I feel very comfortable with eclipse and find it much more simple/clean/user-friendly that Android Studio or intellij. For me I will continue develop with Eclipse, is this a good decision?
Will Eclipse ADT be deprecated when Android studio reach its first stable version?
No. According to Xavier Ducrohet in this keynote the Android team will maintain the work on the ADT (At 00:35).
Why the Android Team started another IDE instead of continue improving the old good ADT ?
I'm paraphrasing Xavier Ducrohet now: He says that by building your own IDE they can improve the workflow for developing Android apps. And to be honest, in my opinion the current version of IntelliJ is a lot faster than Eclipse Helios. You just have a great overall experience by using IntelliJ. This is a matter of personal preference of course.
To be honest I feel very comfortable with eclipse and find it much more simple/clean/user-friendly that Android Studio or intellij. For me I will continue develop with Eclipse, is this a good decision?
Maybe. You shouldn't have to switch, if you don't want to. Like I said before, they will still be maintaining the work on the ADT plugin for Eclipse. But at least give IntelliJ a try. I'm sure you'll be very impressed by its performance.
At this point, I would strongly advise everyone to use Android Studio for android development. Although the ADT plugin for Eclipse is still available, support for it is lacking and the android developer tools team has shifted their focus almost entirely to Android Studio. And quite frankly, Android Studio is an amazing IDE, you should definitely switch, if you haven't already.