I've not really decided on the matter yet, but I'll definitely not be using my Japanese HG as my main, so it would very likely have to wait until the US release, which is quite a ways away, yet. The one thing I'm thinking of doing is not trade them over to HG until I have a specific reason to do so, at the very least. I actually might start anew with HG and train some new Pokemon that I'll only use on there. (after all, I now have some Return-users, and I can't really be bothered to re-boost their happiness every time a new game comes out... -.-;; )
I attempted the same thing with Diamond <--> Platinum and it worked out well for the Pokemon, but terribly for the items. I still have a real hoard of items still on my Diamond; some I would very likely use, such as berries and TMs. Back then, I had no Pokemon that used Return though, so in that sense, it was much easier.