I'm not at all easy at the thought of him parting with Lendl again just yet but, should it come to pass, (and it has done so before), then I also wondered if he might hook up with Boris if the latter is still available. After all, Boris helped Novak to double his number of Slams. Would be fantastic if he could do the same for Andy!
Becker is underrated as a coach. He helped Novak stay motivated until RG was won. It wasn't an easy job to coach a player to play against all time greats like Nadal and Federer, but Becker made it possible. The influence of him on Novak was a crucial one and of course Novak was ready to receive. It worked out perfectly well so far until they split.
I do think Lendl came at a right time in Andy's career but I feel the influence may have worn off. It is also important to make note that Andy is at a completely different stage of his career at the moment. Lendl's need was to help Andy win his first slam, which he did not once but twice (USO and Wimbledon), but that need is no longer there. Now Andy needs a coach who would see him through a few more Slams and Becker just has that kind of precise experience having coached Novak where Andy is right now.
Novak, on the other hand, would be better off with Annacone. Because he is at a final stage of his career so Annacone can definitely see him win a few more because Annacone has the experience to work with greats like Sampras and Federer at that stage of their career.
I don't think either has lost motivation in the true sense. Both are taking time and reflecting back as finally winning RG was a huge deal for Novak, while Andy winning Wimbledon and Olympics for the 2nd time, Rome, Paris, WTF for the first time and ultimately becoming World No. 1 was a huge deal for him. I'd also like to add that because of these reasons both Nadal and Federer got lucky at the AO. If these two were both at the same level as last year, then I am not sure if Nadal or Federer or both would have made the final, let alone one of them winning. I don't underestimate either Nadal or Federer but it was clear that No. 1 & 2 were better players and were the favourites to win the AO. But the above factors turned the tide against them and worked in Fedal's favour.