I don't know why you think the Portuguese might be embarrassed? I can see nothing to be embarrassed about, but if there is then why not the other scenario? It can't be because they failed to catch whoever, they had a year and OG have had a lot longer, loads more people and loads more money.
I think the Portuguese authorities would be embarrassed because it would confirm without doubt that their initial investigation, leading to the making arguidos of the McCanns was a complete cock-up. It would be embarrassing because of how quickly they gave up on the case when there were many leads left un-followed up. It would also prove that "national hero" Amaral's judgement was seriously flawed, that under his and his colleagues' watch they allowed a child abductor to evade justice for many years. The majority of the country apparently is still convinced the McCanns dunnit - how would the country cope with the knowledge that they'd been wrong to be pointing the finger at innocent parents of a missing child all these years? I'd hope they'd be ashamed of themselves, but maybe if they have no shame, then perhaps you're right - no embarrassment either.