If we're counting all sources for such rumors, the probability of the named deal happening is very low. On the other hand, if we're counting only such sources as Bloomberg, Reuters, and the WSJ, the probability is pretty high that the reported discussions are real, even if no deal is ever consummated.
In this instance the source is FierceBiotech, so I suppose the probability is somewhere in between the poles mentioned above.
“The efficient-market hypothesis may be
the foremost piece of B.S. ever promulgated
in any area of human knowledge!”