The Brawly/Bruno connection does not necessarily imply that Bruno would know anything about the Hoenn Pokemon. Brawly could've hailed from Kanto and then settled in Dewford later.
I think I just worded some things oddly. What I'm saying is that we have just as many things that completely screw with that idea as well(of them happening simultaneously), although nobody has really brought many solid pros, if at all; One of the more notable things that opposes the idea is how Team Magma/Aqua's actions weren't even noted in Gen V until B2W2(which shows that Gen III could possibly have happened inbetween the two sets), while they clearly mention their thoughts on why Galactic and Rocket failed in BW.
Trading, etc. have been retconned all throughout the Pokemon games so that's why I put out the idea that those don't really prove a thing when it comes to where a gen is placed. B2W2 are a perfect argument to further show that because you can freely trade/battle between both sets of games regardless of the fact that the latter two happened two years later.
We really don't have anything solid that gives Gen III a specific place is my main point.
As for the whole Brawly/Bruno issue, I'm not even sure why it was brought up(simply knowing someone from other regions a while =/= the main events of their respective regions' games having to take place at the same time. That conversation just turned into a mess really.
From what I've been trying to point out this whole time...I'm just going to ignore some of that and just say that it would be interesting if Gen VI turned out to be more of a prequel, although as of now I think it happens in the future.