The seven ages of man that Jaques describes are the stages of life: from birth and childhood to adulthood, old age, and finally extreme old age. When a person is "sans teeth, sans eyes, sans taste, sans everything," they are close to death.

Sans means "without," so the statement means that at the end of life one is without teeth, without eyesight, and without the ability to taste. Jaques sums this up as without everything.

Jaques is being comically imprecise in this statement. He mixes the literal (old people being without teeth) with the figurative (old people being without eyes.) Their eyes have not literally fallen out like their teeth: he means that they are blind or see with difficulty. Also, while the elderly do become less taste sensitive, it would be more common to note their deafness. Finally, Jaques just gives up and uses the vague word "everything." He is describing how helpless the very old became in a time before medical interventions could help them to a better quality of life.

Shakespeare pokes fun at the lack of finesse Jaques has with words, but Jaques's words show that the Forest of Arden is no magical place. The same process of aging and death that happens throughout the world happens here as well.

Sans is a French word meaning "without," so the given quotation means, "Without teeth, without eyes, without taste, without everything." This is the final line of Jaques' soliloquy from act two, scene seven of As You Like It.

In the soliloquy, Jaques says that the lives of men pass through different stages, much as a play passes from one act to the next. In fact Jaques identifies seven stages in the life of man. The first stage he says is infancy, and the last stage is a return to infancy, bringing man's life full circle. Jaques calls the seventh stage the "second childishness." He says that just as a new born baby begins life toothless, blind, and with no understanding of the world, so too the elderly man ends life toothless, blind, and with no understanding of the world.

This idea of man's life being cyclical is a common idea in Shakespeare's plays. In Hamlet, for example, the eponymous Hero tells Claudius that, "A man may fish with the worm that hath eat of a king, and eat of the fish that hath fed of that worm." In other words, when a king is buried, he will become food for the worms, and a common man may then use one of those same worms to catch his supper.

In As You Like It, Jaques' soliloquy is well timed to create comedy. After he finishes his speech, explaining that old men are very much like new born babies, Orlando enters the stage carrying his elderly servant, Adam. Jaques' soliloquy also links to the theme of change, which is one of the key themes throughout the play. In the play, those characters who enter the Ardenne Forest seem to change dramatically before they leave. Jaques' soliloquy, with its proposed seven stages of mankind, points to this truth that men change radically from one act or stage of their lives to the next.

If you look at the entire speech, Shakespeare gives a quick snippit to show each stage of life.  He starts with the crying infant and progesses to the school-boy, the young lover, the soldier, the political man (justice), the aging man, the ends with the man very near death.  In the line before the quote in your question, Shakespeare implies that men revert to a "second childhood" and "mere oblivion."  He means that as we age we progress from only acting on instinct at birth to go through life gaining more and more, but we end where were began, and then with even less than we began with.  As the previous post noted, "sans" means without.  So at the end of life, man is without teeth (like an infant), without the ability to see (like a child's limited view), and without taste (like a child who only experiences one taste, mother's milk).  With death comes the end of everything -- even those most basic instinctual things we are born with.

What Shakespeare is saying in the line that you cite is that all people eventually die.  In this passage from As You Like It, he has gone through what he says are the seven stages of human (male) life and now he is pointing out that there is one last stage -- death.

The words "sans" means "without."  It is a French word that is often used in English even today.  So he is saying that in the last age of a man, the man is without eyes, taste, or anything else.  He also says that this is the "last stage of all" and that it is the stage that ends a man's "history."   So clearly, he is talking about death.