Im amazed at sheer ignorance of some people actually thinking "how BW is reboot".In what way exactly?
Just like with each previous region past Johto we had:
-Ash leaving all his pokemon taking only PIkachu with him
-Female getting replaced by new one(unfortunately yet again)
-Characters getting new clothes
.Pikachu being reseted like he does at every start.
-.Joy and Jenny are same characters just with new looks.
Pretty much al of above things AG and DP did too.
What was different:
Pretty much only another companion being replaced(Brock)and at start none of older pokemon being seen though thats not entirely correct seing how Pikachu and Meowth are generation 1 pokemon being in BW.
Team Rocket taking their job more seriously with return of Giovanni doesnt make this reboot either.
Reboot as others already said would mean complete clean slate with no connections to past replacing all characters like Digimon or Yugioh did etc.
With current state of things writers changed little more than they did before but that doesnt mean all connections with past has been cut with prof.Oak and Dehlia still existing,Ash and TR being part of show aswell posibillity of other previous companions being seen again from story standpoint reasons existing like DAwn,May,Misty,Brock etc.
It just happened a lot earlier than expected. Who honestly believed May and Dawn wouldn't battle in a Contest? Seriously?
It was the people thinking Misty would meet Dawn that were totally pulling fanfiction.
Mays return was like fanfiction too.I remember people saying how there was no reason for her to come all the way to Sinnoh when she was in Johto being occupied with doing contests.
Writers simply invented whole WallaceCup thing to provide some reasoning behind her visit in DP.
Same could be done for Misty with writers pulling out some reason but they choosed not to.