More like 3 or 4 orders of magnitude, depending on what you count (which languages / articles) and that is leaving aside the talk and other parts of the wiki commons.
It's just 1 order of magnitude, if we're comparing the same language. English Wikipedia has 19,339 articles on philosophy [1]. (Anyone know if there's a resource comparable to SEP in a language other than English?)
If we're talking all philosophy articles in all 291 Wikipedias [2], and (generously) assume that the average Wikipedia has 10% as many philosophy-related articles as English Wikipedia, that's 19,339 * 0.10 * 291 = 562,764 philosophy articles on all Wikipedias. That's 3 orders of magnitude more than SEP's 1,500 articles -- although that's not really comparing apples to apples as we're comparing many languages to one.
