update (06 July 2011): According to Reuters, Tanzania's Natural Resources and Tourism Minister Ezekiel Maige said in a telephone interview with the news agency (published on 01 July 2011): "The Serengeti road project has not been abandoned...we have just revised it. I don't know where all this confusion comes from. [...] The project is still there without a shadow of a doubt. But the road will be unpaved, so there will be no tarmac road or highway traversing through the Serengeti National Park." No good news - it looks like the currently "unpaved" road will eventually become a Pandora's box...
update (29 June 2011): via The New York Times, published on June 27, 2011 : "Unfortunately, the letter announcing Tanzania’s change in plans is too ambiguous to celebrate, and it leaves the ultimate fate of Serengeti unresolved." [...]
Tanzania's government has informed the UNESCO World Heritage Committee that the North Road project through the Serengeti National Park, which would have split the northern part of the Serengeti wilderness and seriously disturbed the migration patterns of animals there, will get reconsidered. The government of the East African country will instead continue with its proposal to build a highway through the north but without the 53 km stretch of gravel road crossing the national park.
According to Serengeti Watch, which campaigns to preserve the Serengeti's ecosystem, Tanzania's decision to scrap the plans to build the highway is no cause for celebration as they expect that development will continue.
Serengeti Watch's interpretation of Tanzania's decision to scrap plans (via their newsletter from 23 June 2011): A battle has been won, but the struggle to save the Serengeti goes on. Roads will still be constructed up to the edges of the park. The pressures on the Serengeti, including a commercial corridor to Uganda, still exist. The highway across the Serengeti has been proposed three times now, and can be raised again. But yes, let's congratulate ourselves on the work we've done.