How close are なりつつある and なっている?


> 語学学習は私の新しい習慣の一部になりつつあるのでしょうか？
>
> "Is learning languages becoming a part of my new daily routine?"

なりつつある here seems similar to なっている... are they often interchangeable? Would I
be able to change them back and forth without changing the meaning of this
sentence much? This is my first contact with this suffix so if anyone has
warnings about its usages or beginner's mistakes, please feel free to espouse.

wwwjdic defines つつある as :to be doing; to be in the process of doing

<http://nhg.pro.tok2.com/qa/kousei-7.htm>




They are not interchangable.

  * `なりつつある`: in the process of becoming 
  * `なっている`: have (already) become 




They are not interchangable.

  * `なりつつある`: in the process of becoming 
  * `なっている`: have (already) become 

