I think they supplement each other. Wikipedia is a great place to go explanatory material; statistics are a part of that but if you are really interested in the numbers behind something you'll probably follow up the citations. Alpha looks to have great potential as a tool for statistical discovery and analysis, but I rather doubt it auto-generate tutorials on what data mean or why they matter.
It would be nice if Wikipedia can improve the quality of its articles by linking to Alpha; I hope Wolfram research won't exert a propriety attitude to its search results, but will make them available with something like a creative commons license to the extent that the original sources are in the public domain.
Quoting Wikipedia is not respectable in an academic context because you are not quoting a primary source, or even a secondary source. You are typically quoting a tertiary or quaternary source. If the article is properly cited, however, it is not difficult to simply quote the original citation.
I expect students who use and quote Alpha as their source of information won't get the same scorn than the ones who quote Wikipedia.
It will be an interesting battle: crowdsourcing vs. proof.