The timeline has been irrevocably altered, and the saga of Star Trek will now unfold differently. Where does that leave the established movies and hundreds of television episodes that followed?
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The timeline is new and separate. The original (insofar as that applies) is still there--in fact, it is the source of the new one (Nero comes from the "original") and we have onscreen evidence that it continues to exist (Spock came after Nero--if Nero's trip to 2233 had "altered the original", then Spock could not have followed him through). It is true that any immediate future on-screen installments of Trek will not return to the "original" timeline, but that does not mean the original is gone (in-universe--I'm not referring to the fact that all the DVDs are still available).
All the preceding adventures of the past 40 years led to the incident that sent Nero and Spock back--the film's story could not occur without those events.