Recently BJD in Orissa snapped ties with BJP, and JD (U) in Bihar is also elbowing BJP for more seats not only in Bihar but also UP. This is a clear reflection of that in this time of coalition, politics is becoming more pragmatic and based on expediency rather than image of a "Elder brother", "omnipotent partner". BJP or even Congress can't be labeled as elder brothers carrying on smaller coalition partners.
In terms of Bihar, there is no doubt that JD (U) is in a commanding position, however I fear that overconfidence does not create the path of perdition for JD (U). I was reading somewhere that Nitish Kumar is keeping all options open in terms of aligning with who ever comes to power in center whether UPA or NDA, I personally feel that this is just a rumor, because, Nitish has carved his niche based on Lalu's misrule, and that should be the raison d etre of his existence at least for one more term.
There should be no alignment, in any way, that relates Nitish to laloo, even if it means being in the same coalition. I know power game has it's own dynamics, but to be a long term player you have to sacrifice, allurements however strong in the short term, and there could be no better enticement than being a part of the ruling party in center.