Spears drops to #2 as sales of Femme Fatale trail off in second week. By Gil Kaufman Adele’s 21 Photo: Columbia Records It’s a bit early to call it a changing of the guard, but British songbird Adele will make a strong case that she is a major force to be reckoned with on the Billboard charts next week when her album 21 retakes the #1 spot. Thanks to sales of 88,000, according to Nielsen SoundScan, Adele pulls the feat off — her fourth non-consecutive week at #1 since the album’s release in late February — while forcing last week’s #1, Britney Spears ‘ Femme Fatale , down to #2. Spears’ highly anticipated new effort suffers a steep drop-off in its second chart cycle , plunging 73 percent on sales of 75,000, for a two-week total of 352,000. In contrast, Adele has pushed past the 1 million mark in seven weeks to notch the best-selling album of 2011 to date. Also losing a significant amount (70 percent) of business in its second week is rapper Wiz Khalifa ‘s Rolling Papers , which falls three spots to #5 on sales of 59,000. Masked rap-rock crew Hollywood Undead scored their best chart debut ever with American Tragedy, which comes in at #4 (66,000), while little-known metalers Asking Alexandria come in at #9 on sales of 31,000. The rest of the top 10: Radiohead , King of Limbs (#3, 67,000); Chris Brown , F.A.M.E. (#6, 51,000); the iTunes Songs for Japan compilation (#7, 51,000); Mumford & Sons ‘ Sigh No More (#8, 34,000); and Kirk Franklin ‘s Hello Fear (#10, 31,000). Jennifer Hudson ‘s I Remember Me slips four spots to #11 as sales dip 46 percent to 31,000, while Rock and Roll Hall of Famer and former Band member Robbie Robertson scores a #13 debut (22,000) for How to Become Clairvoyant, his first studio album in 13 years. Rapper Jim Jones hits #20 with the debut of his latest, Capo (21,000), indie faves The Kills come in at #37 with Blood Pressures (13,000), and superstar DJ Ti