We need search engines. Imagine a person reading an article about a topic he has not studied before. As expected he’ll find many terms which are entirely new for him; how will he know about them, will he straight away to some site to get the meaning of a particular term. But in this case he doesn’t know which sites have info about the particular term. Here Search engine comes at rescue, he/she will just type the word and the search results will show sites or other sources which have information regarding the searched term. So Search engines are of use.

Now, regarding will Google remain a leader in Search market for ever: I think taking into consideration the bear-share search market share Google has at present; it’ll take at least 5 years to some other player to make for some formidable competition.

Rest, God knows better.

No. Others will take over in specialty areas.