The October Q&A from an american board suggested that Hasbro would be releasing Grimlock in the last quarter of 2009. If that is indeed true, I don't think Hasbro AUS will release the JP version - it would limit sales of their own release, and they've only imported JP versions of MP toys that weren't released by Hasbro.
Hopefully Hasbro answer that in their current round (I submitted a Q about it in November), so that we might have confirmation on their next 'MP' figure being Grimlock, before next month.