I think it will be Russia. Croatia just scraped past Denmark yesterday and I think they may have peaked too early, a bit like NZ in 2016 World T20. And with Russia, the team morale will be so high after knocking out Spain and with the fans giving them that extra roar, I think they should be able to beat Croatia to make the semis.
Russia in my view, who will either be runners-up for the tournament or contest the 3rd place play-off. They remind me a bit of South Korea in 2002, an unfancied host nation that have performed above expectations and fed off a wonderful home crowd.