I think it is somewhat thin that Littlefinger should be able to secure a betrothal for his illegitimate daughter to the heir to the Eyrie. IIRC there was some explanation for that regarding money, which is a little bit weak. However...
dianod is correct in that Littlefinger stated his plan to Sansa in AFFC, and it is a solid plan. Not without cost, though, as it would alienate any remaining Lannisters. The gain would be considerable, as he would gain a firm hold of the north through Sansa, a somewhat less firm hold of the Vale through Harry, and a yet again somewhat less firm hold of the Riverlands through his own Lordship of Harrenhal.
Is it his true plan? It does seem so, but with Littlefinger, who knows.
Would that be his endgame? To paraphrase Littlefinger himself, to know how to move a piece, you have to know what motivates them. Littlefinger seems to be callous and egocentric, but it is implied that he is strongly motivated by his love of Catelyn. With Catelyn dead (or undead, as it turns out) he has shifted his desires to Sansa, but the question is if that is something he would have counted on in his long con. I think not.
Remember that this whole mess was started by him. He is literally the spider in the middle of the whole Lannister-Stark web. He made Lysa poison Jon Arryn and send a letter to Catelyn, thereby triggering all the events that lead to war. Littlefinger thrives on chaos, but I highly doubt he could have hoped to win Catelyn, even if Ned died. I somehow do not have the impression that he knew of Sansa beforehand, but rather noticed her when she came to King's Landing with Ned. So, if not love of Catelyn/Sansa, what then?
Is it power he lusts for? It may be. Although he was already fairly high up in power from the start: treasurer and member of the small council is perhaps one of the highest offices in Westeros. As someone (Tyrion?) said, though, Why would a man with a pot of gold want another? Perhaps, but I think there is more.
Littlefinger comes from a (somewhat) humble background, being the son of a minor lord. He is short, does not inspire love or loyalty or trust (except in Lysa, who he deceived and murdered). People (rightly) consider him sleazy and untrustworthy. His biggest love Catelyn spurned him, and he was humiliated by Brandon Stark. I believe Littlefinger wants to win and be acclaimed hero, and win the love of the people, the respect of honourable lords and the love of women (Sansa, perhaps). And also in the meantime, get some revenge on people and houses who he feels have wronged him. In short, I think he wants real love and respect.
It feels like a logical plan from his side. He tried to fight Brandon, but swords are not his best game. He plays the game of thrones. So he sets the kingdom up for chaos and then puts it back together again, and is (possibly) celebrated as a great hero.
I believe, though, that in Sansa, he will have met his match. I do not think she will be as accommodating to him as he thinks. But that's another story. It is interesting to note, however, that Sansa is not yet aware that Littlefinger betrayed Ned. She will be told by someone, I am sure, and I wonder how he will try to fix that. He should realize that this knowledge will forever alienate Sansa.
I also remember some people having theories on Littlefinger having some plans for Daenerys' return. By his own statement, he stopped the small council from hiring a faceless man to kill her, and also he has worked on similar goals as Varys: causing chaos, setting houses against each other. If this was the case, he would have done more for Dany than Varys and Illyrio in securing half the kingdom before she even lands. But seeing as he scarcely seems interested in Dany, or is mentioned in any such connections (unlike Varys and Illyrio), it does not seem likely. Interesting, though, and food for speculation as to what he will make of Aegon's army, and Dany when/if she comes to Westeros on Drogon's back.