Skipness1E,
With the fuel price where it is, wouldn't IB prefer to halve the number of big engines it has chewing fuel? Especially if there were economies of scale from merging some support functions with those of a sister company? Who knows, maybe even other oneworld carriers could get in on the act.
I'd suspect that most of IB's 343s are getting towards the end of their leases and the earlier 346s would be getting on for half-way through. Replacing over the next 5 years or so starts to look feasible.
Then again perhaps like others whose governments have a big stake in their countries' aerospace industries, there'd be too much face lost if the national carrier didn't have some (at least partly) home-grown long-haul heavy metal flying to the ex-colonies...
