Taken over by who? The SEC or EU would never approve of a merger between oil majors. Companies outside our industry obviously don't understand how energy works, so that would be equally dumb. Maybe in another 15 years as big oil continues to shrink, you'll see some consolidation.
The SEC never cares, and the FTC in the USA and EU only care about the downstream. If you look at the last number of larger mergers, BP-Amoco, Arco, Exxon, Mobil, Chevron-Texaco, only the refining and marketing is up for discussion.
By whom, easy XOM. When Exxon bought Mobil for 75 $B, XON was a 175 $B company. Mobil was then the #2 oil company in the US, same as Chevron is #2 today.
Exxon is a 420+ B company, and Chevron 210+ B company. So the current market cap ratio of XOM/CVX is not quite as large as that of XON/Mobil, but it's close enough.
This is a plauzible scenario.
Not. Stock price is being drive by Middle East (have you seen the price of oil lately?); Q2 (thank Bernake); Chevron is weighted toward oil in its portfolio; Obama energy speech was so laughably ineffective and clueless everyone knows that oil consumption x10 is in our foreseeable future.