Certainly the medal play will cause shifts in the victory conditions people choose to play in the GOTM's. I think it mostly won't affect the medal winners, as 'top' players tend to be the ones who have the most free time to put into their games, and thus can be the ones who are able to play all 6 games instead of just the GOTM's. The Cultural medals may be the exception though.
Already the Cultural victories are mostly ignored by GOTM players from month to month, and hopefully the games directed towards them will help give those type of games a boost in player interest. I think it's partially a perception that Cultural victories don't score as well as the other types in the Jason scoring system. With a large number of players directing their focus towards Cultural victories in certain months, that perception should change.
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Discussion of what victory type a player will be pursuing is alright in the pre-game discussion threads. As noted in those threads, once you've started your game, please refrain from making comments about your game in any thread other than the proper spoilers.