Boeing was pressured by, among others, Singapore Airlines to offer the Trent on the 773ER and 772LR but the exclusivity deal put to them by GE was unmatchable by RR even though they were already running a Trent at above 100k/lb. The ability to develop a 115k/lb engine was never the issue. But what goes around comes around and RR now have a de facto exclusivity on the A350XWB, although they never asked for it, because GE won't / can't compete with the 773ER / 772LR by offering an engine on this type. The A350XWB has now outsold the 773ER and 772LR so RR must be smiling in quiet satisfaction. And sales to date of the GEnEX exclusive 747-8 probably means they are relaxed about that decision too. From their point of view, exclusivity isn't always what it's cracked up to be - e.g. A340-500/600.