It's an interesting rhetorical flourish from him coming days before his inauguration, and is being instantly spun by media -- but they may just suck at English too much to notice the nuance involved.
Here are segments of original AP exclusive interview. Ma's phrasing, as quoted: "Ma says 'it is difficult to see the chance for unification talk[s?] even in our lifetimes' because Taiwanese are opposed to China's communist system."
AP summarizes this in it's lead paragraph as: " Taiwan's new leader Ma Ying-jeou says that unification with longtime rival China is unlikely to happen 'in our lifetimes.'"
According to the first link I Ma's office, when explaining the quotation, re-worded it further to this: "We may not see [unification] my life time."
All of which, despite the different wording, mean more or less the same thing. The problem is the translation being used by the Taiwanese media. Check out some of these headlines, many of which mis-translate "unlikely to happen" or "it is difficult to see a chance for" as "impossible," almost making it sound like "over my dead body." Oddly, TVBS's headline is as accurate as the Liberty Times:
馬辦：有生之年不會統一 就是說明台海現狀 《中廣新聞網》
馬稱統一此生不太可能 綠營：應觀其行 《中央社》
馬說一生難見統一 綠委：嘴巴不講 暗地漸統《中廣新聞網》
馬英九：此生不見兩岸統一 馬辦：客觀現實的描述 《中央廣播電台》