I doubt it - Capello made it clear when there was all that business about Beckham's 100th cap that he'd do nothing out of sentimentality, only if the player deserved it, and King's not had enough England caps to warrant a pity call-up.
I think it's simple: King's been one of the best English CBs in the league, particularly on recent form, and Capello's determined to use the best of the resources he has available. I don't think he'd have called him if he wasn't going to play him (there's no point with his at best minimalistic training opportunities), so I think there are two options: 1) he wants him to help England qualify and will play him next Wed even if it means him missing a game for Spurs (which I don't really have a problem with, I'd be really pleased to see him back in competitive international competition), because he thinks he's one of the top CBs, or 2) he wants to play him for the friendly to see how he gets on coming straight into the team (i.e. if he can do it as well for England as he can for Spurs).
If it's the latter, I suspect he'll be using it as an equivalent of a training session for him to see if - if he stays on current form - he can fit into the squad and should be used for future qualifiers, or (quite probably) as cover for the actual cup. I'd say only cover, but don't forget he's been employed successfully as CB and DM, if we were to qualify it'd be useful to have someone in the team who can run out in either of those positions even if only as a sub or in one game.
I'm really pleased about it: Ledley knows his health and isn't going to risk it, the Spurs medics aren't going to let him risk it and according to media they're at the training camp, and Capello's no fool, he's not going to do anything to endanger him, but he's a great player and he doesn't have long left in the game; he deserves to be playing for his country and I'm glad he's been given the chance to do so in spite of the obstacles.