I think the usual bet means that you will profit normally if Argentina wins the first half as expected but you'd get double your profit if Argentina wins by Messi scoring in the first half. I feel the bet is only valid for the first half alone and not the full time taking into account.
Argentina will try to resolve this match as earliest as possible and send alternative players in to give more resting time to their main star players. In World Cup, any injury of a main star player can affect a whole team in remaining matches and Argentina will surely not want to face with such unexpected injuries. Messi is very important with their team and they will try to protect Messi as best as possible.
Austria certainly will not play this match to lose, so they will try their best but Argentina are simply at a higher level. Austria will try but it's unlikely that they will be able to get any points from Argentina in the upcoming match.
