I would imagine that they are pleased with the cost/effectiveness of the Super Hornet and plan on extending its duty span for as long as they see it fitting the role(s) they have. There aren't that many people who are trained on servicing and keeping bleeding edge tech air-worthy. There's a benefit in keeping what you have, especially when it works. If the Aussies (for example) saw a future or imminent need for a stealthier aircraft, they would probably be asking for them. But letting the US bear the cost of development, shakedown, refinement and everything else associated with bleeding edge tech... that's a wise decision. Now, if they (still speaking of the Aussies) considered Chinese expansion in the region to be an issue/challenge that they wanted to meet? Then they might express interest. But I don't believe that they have.