Strange house is the same as the old haunted mansion from D/P/Pt. The ghost girl from there is the same one from the bridge in B/W and possibly the same ghost girl from D/P/Pt. She mentions in the mansion that she had to move to another far off region which is why she left her pokemon alone in Unova.
Coincidentally its the same story that the anime used for the pink haired chick from D/P/Pt. One of the ones that you get to team up with in Gible's cave under the Sinnoh Cycling Road.
Speculating leads to finding facts to support the speculation. If you hate when people do that then you hate speculating as a whole. The point to finding hints it to find proof of the next games coming out.
As for the item, I don't see that as a valid point. Black and White were a revival for Pokemon overall. They even seem to be pushing this fact with a lot of their new merchandise standards. Both Pokedexes released (3DS and App) start off with Unova only. (For the App you have to buy extra upgrades to unlock the other regions)
You also can't deny that they were infact working on HarmoKnight while B2W2 was in production. Gamefreak makes other games. It can be a non-Pokemon related videogame.
As for Tilesets, B/W/B2/W2 doesn't use old tilesets. The tile sets from B/W/B2/W2 are rendered sets while all of them before Gen 4 aren't so all the tiles for Gen 5 are remade tiles. If they bare any resemblance to tiles from any game older then that's a coincidence. They recycle the same tiles and improve them every generation. Labratories all use the same tile sets just updated to meet the standards of the game.
The PC chick references Bill when she gives you an Eevee. You don't see people screaming for Kanto remakes again.