One look at me and most Catalans assume I'm a guiri who might know a bit of Spanish but certainly won't know Catalan
One luxury I predict Catalans will gradually lose as Catalonia opens up to the world is that of switching into the Catalan language when they don't want others to understand what they're saying. Obviously, that presupposes two things: that more foreigners coming here will learn Catalan and that the language will survive internationalisation, both of which I'm prepared to bet will happen.
There are times when it happens quite innocently; people here are so bilingual that conversations and even individual sentences often interchange languages for communicative reasons we don't have time to go into here. But it can also be used furtively. The first time I remember hearing about this was a curious story involving Bobby Robson's tenure at Barça. Robson had demanded José Mourinho move with him to the Camp Nou as his interpreter. Urban myth has it that in meetings with Barça's president and vice president José Luis Nuñez and Joan Gaspart, respectively, the latter two would switch into Catalan when they didn't want Robson and Mourinho to understand, when in fact Mourinho understood well enough due to the fact that he is Portuguese, and Catalan and Portuguese are sufficiently similar for speakers of those languages to understand one another. Far from excluding Robson from the conversation, then, they were unwittingly giving him all the information he needed to defend himself against any future machinations (let's just say Nuñez and Gaspart weren't exactly known for being the most scrupulous of actors).
Is the story true? I can't honestly say, but I do admit to using this tactic myself with my wife when we've been on holiday in the UK or Italy and wanted to communicate without others understanding, usually to poke fun at those around us. One example was when members of our tour group in Italy were doing something that annoyed me and I made jokes about them to my wife in Catalan. It's a tactic that, although somewhat disingenuous, gives users the protected feeling that no matter what they say, they won't be understood by third parties. To be fair, it's used by anyone to their advantage in situations where their language is unknown, which also makes it a tactic that monolingual speakers - and many of my compatriots sadly fall into this category - cannot use.
It can also backfire. One look at me and most Catalans assume I'm a guiri who might know a bit of Spanish but certainly won't know Catalan. The place where it's been most to my advantage has been playing poker in the casino, where there are plenty of other guiris who definitely don't speak Catalan and so the assumption is a fairly safe one. In that situation, where the more information you have on your opponents, the greater your chances of winning, it's of great benefit to listen to locals discussing the game confident that others around them can't follow what they're saying. Only a fool would give up such an advantage, and I obviously keep schtum. So beware my Catalan friends, the days of secretive chat may be coming to an end.