I think the very high premium paid by TI for a wilting NatSemi is questionable at best. The only thing I can take from it is that TI is desperate to find volume parts for it's fabs, which - when they get their 300mm up and running well will need high volume parts to make it cost effective, since higher performance, but lower volume parts might need a fab run one a year or less.
I really don't see this acquisition being accretive for years, if ever.
That said, the guys who may be worried are the sub mega IC guys - particularly ST (and NXP) ( or very long shot -Intel) to become potential buyers to try to put themselves back in the same scale as a TI (or on the Intel case, to expand and diversify).
Linear Technology and ADI are the two pioneers offering almost similar products in their portfolios, hence I think from the perspective of these respective businesses, it won't be beneficial to merge, as there will be a good chance of product cannibalization.