Free Paella
If Telefonica have their right-thinking hats on then they will do something along the lines of Vodafone's Passport, or better. Not quite roaming for no extra charge, but the notion of using the contract bundled minutes while abroad is very attractive, even if there is a 70p "connection" charge. But you have to be on Voda's foreign network to use this.
Again, looking at Vodafone for an example, their Stop The Clock begs the question "If one network can give away 57-in-any-60 off-peak minutes to any national number then why can't the others?".
Whatever Telefonica/O2 do, they need to avoid being gimicky, hard to understand, or limited in scope (i.e. T-Mobile's Mates Rates).
I rather think that what happens will largely depend on whether or not Telefonica have been able to divest themselves of the traditional European PTT mentality displayed by the mobile ops to date. They [all] need to be much more innovative with their tariffs and network offerings which will generate increased revenue through increased usage.