Very great find Chatte! I love how you used many examples within your explanation, giving it a relatively better feel for those that have a harder time understanding without the use of pics. I fully agree with everything you have posted and, having Sakura being the main heroine, it makes perfect sense. Kishimoto would not create a female protagonist that cannot hold her own for this long unless he has a plan devised for her. I find it funny how so many people bash Sakura from the use of her new power already without even getting past the fact that she didn't even get the chance to use the full power of it and only executed 1 little punch, not even getting through to them that she just barley begun to fight yet. It shows the ignorance of those fans and cannot put it past them that Sakura is getting screentime and upgrades for herself. I am just wondering how Sakura will fall into place with that symbol. Is it indicating she is related to Hashirama himself? or perhaps is she part of a clan? Afterall, the only ones depicted so far with the use of the yin seal have had Uzumaki blood in them, so I wonder how this falls into place with Sakura? Either way, makes you really think about how close they (Hashirama and Sakura) do resemble one another in ways.
I also thought it was interesting to note the symbol on Hashirama's head when in his mode, was also the same that Sakura wears on her outfit and in her room. I feel that being the main character she is, Kishi knows he must upgrade her relatively quickly in order to keep his audience with her on the move. She has been due for a change of pace for a while now, and as I have stated earlier in my other posts about her, that being the main character that she is and training with a woman who, is not only the 5th Hokage who also specializes in being a Sannin, but also has Senju DNA in her. Sakura is going to come out powerful no matter the outcome. If your theory is true, then people better prepare for a very powerful Sakura which, would explain all the talk she has been executing saying that she has "finally caught up with them"
I personally thoroughly enjoyed all of your examples and thoughts on this matter regarding Sakura's updated power, and even thought it was rather long, it kept me interested and on my toes to keep reading. I am a fan of Sakura myself, and I hope that she does indeed get something good for her that will have people look at her in a better light than the one she is already displayed in. Great job on this thread and your theory on Sakura!