Probably not since US and European Pokémon Company outlets are advertising January 8th as well.
I'd bet on the announcement being at a reasonable hour in all of these time zones.
I don't think it's going to be a simultaneous announcement. It would be kind of dumb to punish Japanese fans just so fans in America and elsewhere can learn about this news at the same time.
I think the respected websites for each country will still post the news on the 8th in their local time, but most of us will know what it is ahead of time due to the Japanese reveal.
I think the Japanese website will post it at noon on the 8th which will be around Monday evening in North America.