If some investors/traders here sold because they made money, good for them. Making money is a good thing.
But unless Ariad mgmt. scared off Baxalta with a hint of what they would be accepting, then it would be a bit unusual to think that Baxalta would think they could lob one offer over the transom and that would be it. The only possible reason would have been to see how their market price (to Shire) would have been affected, and that result wasn't very good. If Baxalta is serious, we'll see another offer.
Whether Baxalta proceeds or not doesn't so much matter to the eventual b/o price I think most believe is necessary. I think it could take a bit more time for the drugs to progress but of course, would be ecstatic if it was done earlier than later.
Might take a slightly bigger buyer than Baxalta though. In the meantime, these b/o offers raise the pps and don't totally collapse with no deal done. Ariad is in play, and that means some of a b/o premium will remain in the pps until Ariad is bought.
